Sardar B Alam

Christopher R Andersen

Federico Panciera

Aage A S Nilausen

Ole Hansen

Frances M Ross
email: fmross@mit.edu

Kristian Mølhave

In situ modification of individual silicon nanowires reveals transition in charge transport mechanisms

Keywords: nanowire, electronic transport, in situ measurements, TEM, surface oxidation

Correlating the structure and composition of nanowires grown by the vapour-liquid-solid (VLS) mechanism with their electrical properties is essential for designing nanowire devices. In situ transmission electron microscopy (TEM) that can image while simultaneously measuring the current-voltage (I-V) characteristics of individual isolated nanowires is a unique tool for linking changes in structure with electronic transport. Here we grow and electrically connect silicon nanowires inside a TEM to perform in situ electrical measurements on individual nanowires at room temperature and high temperatures and upon surface oxidation. As-grown, the oxide-free nanowires have nonlinear I-V characteristics. We analyse the I-V measurements in terms of both bulk and injection limited transport models, finding Joule heating effects, bulk-limiting effects for thin nanowires and an injectionlimiting effect for thick wires when high voltages are applied. When the nanowire surface is modified by in situ oxidation, drastic changes occur in electronic properties. We investigate the relation between the observed geometry, changes in the surface and changes in electronic transport, obtaining information for individual nanowires that is inaccessible to other measuring techniques.

Introduction

The electronic properties of nanowires grown by the vapour-liquid-solid (VLS) mechanism are sensitive to fine details of the nanowire composition, structure and surface. For a wide range of VLS nanowire applications, for example in logic [START_REF] Cui | High Performance Silicon Nanowire Field Effect Transistors[END_REF][START_REF] Weber | Silicon-Nanowire Transistors with Intruded Nickel-Silicide Contacts[END_REF], solar cells [START_REF] Czaban | GaAs Core-Shell Nanowires for Photovoltaic Applications[END_REF][START_REF] Krogstrup | Single-nanowire solar cells beyond the Shockley-Queisser limit[END_REF], optoelectronics [START_REF] Duan | Single-nanowire electrically driven lasers[END_REF][START_REF] Koester | High-Speed GaN/GaInN Nanowire Array Light-Emitting Diode on Silicon[END_REF][START_REF] Breuer | Suitability of Au-and Self-Assisted GaAs Nanowires for Optoelectronic Applications[END_REF], and biological [START_REF] Zheng | Multiplexed electrical detection of cancer markers with nanowire sensor arrays[END_REF] and chemical [START_REF] Demontis | Conductometric Sensing with Individual InAs[END_REF] sensing, achieving the required device performance depends on careful consideration of nanowire composition and surface structure and the interface between the nanowire and the rest of the device. However, determining the structural details of individual nanowires, such as the presence of defects and the surface condition, and relating this to the electronic properties after device fabrication is a challenging task. In situ transmission electron microscopy (TEM) has been a vital tool for visualising and understanding the physical processes involved in the growth of nanowires by the VLS mechanism [START_REF] Ross | Controlling nanowire structures through real time growth studies Reports[END_REF]. Furthermore, in situ TEM has also been able to probe the electrical properties of nanowires inside the TEM while simultaneously recording the structure at high spatial resolution [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF][START_REF] Nam | Electrical wind force-driven and dislocation-templated amorphization in phase-change nanowires[END_REF][START_REF] Chiu | Copper silicide/silicon nanowire heterostructures: In situ TEM observation of growth behaviors and electron transport properties[END_REF]. Such in situ measurements can enhance our understanding of nanowires by correlating composition and structure with electrical characteristics, generating information that is not accessible using other measuring techniques [START_REF] Canepa | Situ TEM Electrical Measurements Controlled Atmosphere Transmission Electron Microscopy[END_REF].

In this work, we have grown and electrically characterised gold-catalysed silicon nanowires inside an in situ TEM with ultra-high vacuum (UHV) at the sample area. We used microcantilever based samples that allow us to grow individual nanowires in a configuration where they are electrically connected at the two ends. We could therefore perform current-voltage (I-V) measurements without exposure to ambient atmosphere on an oxide free nanowire, and then modify the structure and measure again. Figure 1a shows schematics of a sample, a microfabricated chip with Joule heated monocrystalline silicon cantilevers [START_REF] Kallesøe | Measurement of Local Si-Nanowire Growth Kinetics Using in situ Transmission Electron[END_REF] that form the substrate for epitaxial growth of the nanowires. Such chips have been used to study the creation of silicon nanowire devices [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF] and several migration [START_REF] Alam | Creating New VLS Silicon Nanowire Contact Geometries by Controlling Catalyst Migration[END_REF] and high electric field phenomena [START_REF] Panciera | Controlling nanowire growth through electric field-induced deformation of the catalyst droplet[END_REF]. Here, the nanowires are grown between two adjacent but electrically isolated microcantilever heaters to form a suspended bridging nanowire [START_REF] Alam | Creating New VLS Silicon Nanowire Contact Geometries by Controlling Catalyst Migration[END_REF] (Figure 1b). With this setup, we can measure the I-V characteristics of the as-grown nanowire under vacuum at room temperature and higher temperatures. We can also introduce oxygen into the sample region of the TEM in order to study the influence on transport of having oxidised the surface. The experimental setup is described in more detail in the Supporting Information.

Our in situ measurements show that nanowires exhibit nonlinear I-V curves (Figure 1c) that depend on the nanowire diameter and surface chemistry. In the following discussion, we introduce a range of nonlinear transport models before analysing our data and assigning the model that best fits the in situ measurements.

Transport models for nanowires

Ohmic behaviour and Joule heating

At low voltages, a semiconductor will typically follow an Ohmic behaviour where the I-V curve is linear. One source of non-linearity in I-V data is self-heating, in which the increase in temperature due to Joule heating changes the electrical resistance. A temperature increase will decrease the resistance of an intrinsic semiconductor, typically with a strongly nonlinear temperature coefficient of resistivity (TCO). The resistance of an extrinsic (doped) semiconductor, over a limited temperature range, will vary linearly with temperature (positive or negative TCO); but at higher temperatures, it may behave as an intrinsic semiconductor. Since nanowires in this work are suspended, resistive self-heating could lead to considerable temperature increase.

A model combining Ohmic conductance with resistive heating has been described by Mølhave et al. [START_REF] Mølhave | Transmission electron microscopy study of individual carbon nanotube breakdown caused by joule heating in air[END_REF]. As a rough approximation, we may assume a parabolic temperature profile along the length of the nanowire with peak temperature in the center. Resistive heating of the nanowire can lead to linear dependence of either resistance or conductivity with temperature. A linear resistance dependence will produce a linear plot of V/I vs. power IV, while a linear conductivity dependence will give a linear plot of I/V vs. VI. -as seen, for example, in carbon nanotubes [START_REF] Mølhave | Transmission electron microscopy study of individual carbon nanotube breakdown caused by joule heating in air[END_REF].

Several other possible transport mechanisms can also lead to nonlinear I-V characteristics. These include bulk-limited models including space charge limited current and Poole-Frenkel effect and injection limited models of Schottky and Fowler-Nordheim effects. These models are illustrated in Figure 1d-g and summarised in Table 1.

Bulk-limited current models

Space charge limited current (SCLC) dominates when the injected charge density is higher than the thermal equilibrium density of carriers [START_REF] Lampert | Theory of Space-Charge-Limited Currents in an Insulator with Traps[END_REF]. All injected electrons (or holes) are then transported via the conduction (or valence) band. This is typical for insulators, wide-gap semiconductors and poorly conducting polymers [START_REF] Simpkins | Space-charge-limited currents and trap characterization in coaxial AlGaN/GaN nanowires[END_REF]. The SCLC I-V relations can be divided into three regimes [START_REF] Lampert | Theory of Space-Charge-Limited Currents in an Insulator with Traps[END_REF]:

 A low bias Ohmic regime (I ∝ V)  A high bias SCLC regime following a power law (I ∝ V a ), with exponent a = 2, when the material is trap-free as formulated by Mott-Gurney [START_REF] Mott | Electronic processes in ionic crystals Electron[END_REF]. If the material has traps with an exponential distribution of energies as described by the Mark-Helfrich equation [START_REF] Mark | Space-Charge-Limited Currents in Organic Crystals[END_REF], a > 2; this situation is illustrated in Figure 1d. The injected carriers will then be partly consumed to fill up the trap levels (Et), which lowers the current.

 An intermediate voltage regime between the two with an exponential increase near the trap-filled limit voltage [START_REF] Lampert | Theory of Space-Charge-Limited Currents in an Insulator with Traps[END_REF]. The SCLC behaviour has previously been reported for silicon nanowires decorated by TiO2 nanoparticles [START_REF] Rasool | Charge injection and trapping in TiO2 nanoparticles decorated silicon nanowires arrays[END_REF], coaxial AlGaN/GaN nanowires [START_REF] Simpkins | Space-charge-limited currents and trap characterization in coaxial AlGaN/GaN nanowires[END_REF] and InAs nanowires [START_REF] Alagha | Space-charge-limited current in nanowires[END_REF]. The two mechanisms, Ohmic and SCLC, are both bulk-limited mechanisms because the dominating conductance is via the bulk of the nanowire.

Another bulk-limited conductance model is due to the Poole-Frenkel (PF) effect, which is seen in materials with a large number of closely spaced defects or impurities. The carriers then reside on the defect sites and hop from one site to another, as illustrated in Figure 1e [START_REF] Frenkel | On Pre-Breakdown Phenomena in Insulators and Electronic Semi-Conductors[END_REF][START_REF] May | Field emission from chemical vapor deposited diamond and diamond-like carbon films: Investigations of surface damage and conduction mechanisms[END_REF][START_REF] Sze | Physics of Semiconductor Devices[END_REF]. The PF model has a characteristic energy barrier φ (Figure 1e), which is the energy needed to overcome the coulomb potential of the trap sites. If the defect sites are too far from each other, the hopping mechanism cannot keep up with the applied electric field [START_REF] May | Field emission from chemical vapor deposited diamond and diamond-like carbon films: Investigations of surface damage and conduction mechanisms[END_REF][START_REF] Murgatroyd | Theory of space-charge-limited current enhanced by Frenkel effect[END_REF] resulting in a transport mechanism that combines filling the traps with charge carriers and the hopping mechanism, in other words, a combination of SCLC and the PF effect. When the defect density is high, an overlap of the columbic potentials of the defect sites will lower the barrier of the carrier hopping, leading to transport defined by Hill's law [START_REF] May | Field emission from chemical vapor deposited diamond and diamond-like carbon films: Investigations of surface damage and conduction mechanisms[END_REF][START_REF] Hill | Poole-Frenkel conduction in amorphous solids[END_REF].

Injection-limited current models

The current can also be injection-limited, for instance, if the carriers pass through a metal-semiconductor interface [START_REF] Chiang | Electronic conduction mechanisms in insulators[END_REF]. The insert in Figure 1b shows a situation where nanowire growth was terminated in a way that creates a residual gold section with two gold-silicon interfaces. Furthermore, the nanowire surface is also decorated by gold: growth is catalysed by a gold droplet which is known to leave roughly a monolayer of gold on the sidewalls at the low disilane pressures used in the UHV-TEM [START_REF] Wiethoff | Au Stabilization and Coverage of Sawtooth Facets on Si Nanowires Grown by Vapor-Liquid-Solid Epitaxy[END_REF][START_REF] Hertog | Control of Gold Surface Diffusion on Si Nanowires[END_REF]. The presence of a gold layer on the surface not only provides a possible transport

Model

Current-voltage relation Ordinate Abscissa Mechanism Ohmic (+ SCLC at Low field)

I ∝ V I V Bulk-limited Ohmic + resistive heating I ∝ V/(R+cV 2 ) I/V IV Resistive heating SCLC (High field) I ∝ V n (n≥2) ln(I) ln(V) Bulk-limited SCLC + PF I ∝ V 2 exp(aV 1/2 /kT) ln(I/V 2 ) V 1/2 Bulk-limited Poole-Frenkel (PF) I ∝ V sinh(aV 1/2 /kT) Sinh -1 (I/V) V 1/2 Bulk-limited Hill's law I ∝ b sinh(aV/kT) Sinh -1 (I) V Bulk-limited Schottky emission I ∝ exp(aV 1/2 /kT) ln(I) V 1/2 Injection-limited Fowler-Nordheim I ∝ V 2 exp(-a/V) ln(I/V 2 ) 1/V Injection-limited
Table 1 -Transport model overview adapted from ref. [START_REF] Gonon | Electrical conduction and deep levels in polycrystalline diamond films[END_REF] with resistive heating model from ref. [START_REF] Mølhave | Transmission electron microscopy study of individual carbon nanotube breakdown caused by joule heating in air[END_REF].

path via the metal surface but could also affect transport through the bulk silicon nanowire through both band bending leading to formation of a depletion region at the surface layer [START_REF] Sundararajan | Electron transport properties of individual gallium nitride nanowire decorated with gold nanoparticles[END_REF] as well as by the introduction of deep traps [START_REF] Hertog | Control of Gold Surface Diffusion on Si Nanowires[END_REF].

Another mechanism for injection-limited transport is thermionic emission (TE) involving only the carriers that have the energy to overcome the Schottky barrier. This contributes to the current flow (Figure 1g) at the gold/silicon interface at gold particles or regions on the surface (or at the Au section in Figure 1b, if present). At low bias, the electrons cannot cross the barrier leading to a high resistance, while at high bias, they can cross leading to a low differential resistance. TE is strongly temperature dependent, as higher temperature will increase the kinetic energy of the carriers [START_REF] Zhang | Current-voltage characteristics and parameter retrieval of semiconducting nanowires[END_REF]. TE leads to a rectifying effect causing an asymmetric I-V behaviour when sweeping between positive and negative biases. However, for symmetric junctions as the metal-semiconductor-metal configuration that we see experimentally, TE should produce a symmetric I-V curve [START_REF] Sze | Current transport in metal-semiconductor-metal[END_REF][START_REF] Elhadidy | Symmetrical current-voltage characteristic of a metal-semiconductormetal structure of Schottky contacts and parameter retrieval of a CdTe structure[END_REF]. TE transport has been reported for various examples of metal-semiconductor contacts such as Au nanoclusters on hexagonal silicon carbide [START_REF] Ruffino | Size-dependent Schottky Barrier Height in self-assembled gold nanoparticles[END_REF] and Al-Ge nanowire heterostructure [START_REF] Kral | Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures[END_REF]. TE transport solely via the bulk semiconductor has also been reported for GaN nanowires decorated with Au nanoparticles [START_REF] Sundararajan | Electron transport properties of individual gallium nitride nanowire decorated with gold nanoparticles[END_REF] and may be similar to what we may be observing here for Au-decorated Si nanowire.

Field emission (FE), also known as Fowler-Nordheim (FN) injection, is similar to thermionic emission in the sense that it has an energy barrier, which must be passed before the current can flow. However, instead of jumping over the energy barrier, the electrons tunnel through the (thin) barrier as illustrated in Figure 1g [START_REF] Fowler | Electron emission in intense electric fields[END_REF]. A relevant study showing FN injection [START_REF] Alkhatib | Morphology dependent electrical transport behavior in gold nanostructures[END_REF] involves conductance in thin gold films with separated grains that lead to the tunneling effect.

An overview of the I-V curves expected for the different conduction models is summarised in Table 1. With the ordinate and abscissa given in the table, straight-line plots should result if the I-V data fits the model. Each model has a unique signature in theory, while measurements often show mixed behaviour.

Matching data to the models

Since nanowires are grown and electrically connected inside the TEM under vacuum, they do not have an oxidised surface, gated substrate, or other sources of contamination that can come from exposure to ambient atmosphere. Hence, our experimental setup, unlike typical ex situ probing, allows us to measure I-V curves on individual pristine, oxide-free nanowires with epitaxial contacts while simultaneously imaging the nanowire for signs of physical transformation or deliberate modification during the measurements.

However, TEM imaging requires irradiation of the nanowire by an electron beam hence the influence of the beam on the in situ electrical measurements must be considered.

Irradiation of the silicon nanowire by high-energy electrons can generate electron-hole pairs and trapped electrons that can charge insulating regions and interfaces. In principle (although unlikely at the 10 -10 Torr pressure range of the UHV-TEM), the e-beam can also generate radicals by radiolysis of trace amounts of gas present in the vacuum and these radicals can react with the nanowire surface. We investigated the influence of the e-beam by performing multiple measurements, summarised in Figure S2, on a nanowire with the beam on and off. We found no trend to indicate that beam exposure alters the transport properties of nanowires in our experiments.

In situ electrical characterisation of pristine nanowire bridges

The length of the nanowires was defined by the cantilever gap (approximately 2.5 µm), so the effect of wire diameter, contact composition, and surface treatment are the experimental parameters that can be varied. The wires had resistances of a few M, making the cantilever lead resistance (a few k) negligible. The nanowire-to-cantilever spreading resistance (~20 k) is also negligible. Three types of nanowires were characterised in this study. Small diameter nanowire (NW1) with a diameter of ca. 50 nm and Si-Si contact (Figure 2a), and large-diameter nanowires with a diameter of approximately 100 nm with a Si-Si contact (NW2), Figure 2b, and a Si-Au-Si contact (NW3), Figure 2c, respectively.

Model for small diameter nanowire

We first discuss the nanowire NW1, with a diameter of ~50 nm, that was connected at one end via a narrow neck created by electromigration of Au contact during Si-Si contact formation [START_REF] Alam | Creating New VLS Silicon Nanowire Contact Geometries by Controlling Catalyst Migration[END_REF]. Figure 2a shows the structure and I-V curve measured by sweeping from -4 V to 4 V. NW1 does not show an Ohmic behaviour. Joule heating effects can also be ignored as the temperature increase is below 10 K as shown in Figure S3. The analysis for the simple resistive heating model is given in Figure 3a and it does not show a linear behaviour of conductivity even for the low bias measurement thus verifying that Joule heating is not responsible for the non-linearity. The nonlinear behaviour must therefore come from other transport effects. The data are re-plotted with the four bulk-limited transport models in Figure 3b such that a straight line would show that the I-V data fits one of the models. The corresponding fitting parameters and statistical results are summarised in Table S1 in Supporting Information. We observe straight line fits for both the SCLC and PF models, and a coefficient of the SCLC fit that is close to 2 corresponding to trap-free SCLC behaviour. However, the nanowires grown in situ are expected to be covered with a monolayer of gold, introducing deep traps as mentioned above. For a thick nanowire with a diameter of ~250 nm, it has been argued that conduction is limited by bulk transport effects [START_REF] Acharya | Poole-Frenkel Transport in Gold Catalyzed VLS Grown Silicon Nanowires[END_REF][START_REF] Acharya | What causes Poole-Frenkel transport in VLS grown silicon nanowires?[END_REF]. Considering a thinner wire, the deep traps introduced by the surface cannot be ignored as easily. Therefore, it is more likely that transport is dominated by a PF mechanism for the narrow nanowire. This conclusion is consistent with silicon nanowires examined elsewhere [START_REF] Acharya | Poole-Frenkel Transport in Gold Catalyzed VLS Grown Silicon Nanowires[END_REF][START_REF] Acharya | What causes Poole-Frenkel transport in VLS grown silicon nanowires?[END_REF], although in that case bulk crystal defects were proposed to cause the traps instead.

Models for large diameter nanowires

We now discuss the two wider nanowires, NW2 and NW3, with diameters close to 100 nm (but with different contact structures). Both wires show I-V curves with an Ohmic behavior for voltages smaller than 3V (Figure 1c inset). This allows us to measure their resistance over this range as 1.25 -2.5 MΩ. The fitting parameters and statistical results of the I-V curve fits are summarised in Table S2 and Figure S5. Nanowires grown in the UHV-TEM are expected to be unintentionally p-doped, according to Ref. [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF], with p-dopant level estimated to be in the range of 10 15 -10 16 cm -3 [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF]. Hence, the nanowires will form a p + -p-p + junction with the p + doped cantilevers that are boron doped to 3 x 10 17 cm -3 . The dopant atoms in the nanowires may come from impurities in the disilane (typically such gases have trace amounts of diborane) and/or from the doped cantilever heater at the initiation of growth. This can occur because the AuSi droplet initially forms a eutectic melt with Si from the substrate (cantilever) and the doping of the substrate may therefore end up in the nanowire. The resistance reported above corresponds to an effective hole concentration of 2-4 x 10 16 cm -3 , assuming the mobility is constant at 450 cm 2 /Vs and the nanowires are pristine [START_REF] Jacoboni | A review of some charge transport properties of silicon[END_REF]. This can be compared to the doping of nanowires grown under similar conditions. Kimukin et al. [START_REF] Kimukin | Surface depletion thickness of p-doped silicon nanowires grown using metal-catalysed chemical vapour deposition[END_REF] studied intentionally doped but oxide-free gold catalysed VLS silicon nanowires of similar diameter grown in a chemical vapour deposition chamber in which no surface monolayer of gold is expected because of the higher silane pressure. These nanowires showed a resistance of 600 kΩ, which, correcting for length, corresponds to 250 kΩ. Hence, the resistance of our unintentionally doped NWs is larger by a factor ~4 than reported literature.

A high temperature (500 ± 10 o C) measurement in the range 0 V to -1.5 V was also obtained for another nanowire (NW4) and agrees well with an Ohmic fit (Figure S7 and S8) giving a resistance of 0.08 MΩ. The decrease in the resistance at high temperatures is by a factor of 25 compared to the room temperature measurements. A final nanowire (NW5) measured at the eutectic temperature of 363 o C (Figure 1c and S7) also shows Ohmic behaviour at lower voltages with a resistance of approximately 0.37 MΩ. The reduction in resistance at increasing temperatures may be explained by a change in dominating carriers. At higher temperatures, the sample may become intrinsic and the electrons have higher mobility than that of the extrinsic holes. At 500 o C, the intrinsic carriers will dominate the bulk charge transport [START_REF] Green | Intrinsic concentration, effective densities of states, and effective mass in silicon[END_REF].

Above 3V, nanowires NW2 and NW3 both exhibit nonlinear behaviour. The temperature profile is likely to be important under these conditions. For NW2, the power used is up to 0.8 mW, resulting in an expected temperature increase of almost 250 K at the centre of the wire as shown in Figure S3. For NW3, greater than 100 K rise is expected at the center (Figure S3). Both wires show linear plots of conductivity with power (Figure 3a), indicating that a Joule heating effect is present. The temperature increase from resistive heating will present. The temperature increase from resistive heating have an impact on Ohmic transport, but it will also affect the different PF models and Schottky emission although not the FN effect. The following analysis should therefore be taken with care since temperature affects most bulk transport models. To avoid effects from a transition region, we apply the models above 5 V where the nonlinear behavior shows clearly.

The two large diameter nanowires, NW2 and NW3, do not indicate SCLC behaviour as their exponent is < 2, as reported in Table S1. Nor do they fit the Poole-Frenkel and Hill's laws, as illustrated in Figure 3c and Figure S6. The poor fits indicate that the behaviour at higher voltages is not dominated by the bulk-limited models. Hence, at high voltages we consider injection-limited currents that arise from gold on the surface of the nanowires. (Only NW3 has a Si-Au-Si region so this cannot explain both sets of results.) We consider the effects on transport [START_REF] Sundararajan | Electron transport properties of individual gallium nitride nanowire decorated with gold nanoparticles[END_REF][START_REF] Alkhatib | Morphology dependent electrical transport behavior in gold nanostructures[END_REF][START_REF] Zhu | Temperature dependent resistance and cryogenic microwave spectroscopy of Au decorated silicon nanowires[END_REF][START_REF] Shekhar | Electrical transport properties of peptide nanotubes coated with gold nanoparticles via peptide-induced biomineralization[END_REF] of either ~ 1 monolayer of gold on the surface, as expected for nanowires [START_REF] Wiethoff | Au Stabilization and Coverage of Sawtooth Facets on Si Nanowires Grown by Vapor-Liquid-Solid Epitaxy[END_REF], or small (5-10 nm) gold islands, also known to form during contact [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF]. The TEM resolution in our experiments does not allow for confirming the presence of a monolayer, but TEM of oxidised wires (Figure S10) does indicate the presence of gold in some form on the nanowire surface, as described later.

Gold on the surface can bend the semiconductor energy bands [START_REF] Sundararajan | Electron transport properties of individual gallium nitride nanowire decorated with gold nanoparticles[END_REF], which can lead to thermionic emission for a semiconductor at high voltages. Another source for injection-limited conductance is if current passes across the surface via the Au monolayer at high voltages. The monolayer of gold can have sufficient separation between the gold atoms that an injection-limited current will appear [START_REF] Alkhatib | Morphology dependent electrical transport behavior in gold nanostructures[END_REF]. In the case of less than a monolayer of gold coverage, the separation of individual gold atoms leads to tunneling.

As was discussed in Table 1, TE will produce a straight line when plotting ln(I) vs V 1/2 , while FN emission will give a turning point at a characteristic voltage when plotting ln(I/V 2 ) vs. 1/V with a negative slope for increasing 1/V (decreasing voltages). Below the barrier, the curve will have a logarithmic growth. The characteristic turning point from FN emission is indeed visible for both NW2 and NW3, i.e. the Si-Si and Si-Au-Si contacts, in Figure 3de. Similar behaviour is seen for NW5 at 363 o C as illustrated in Figure S9. However, at high voltages, the slope is not negative but rather positive, which indicates that transport is not by FN tunneling via the surface layer at high temperature [START_REF] Pananakakis | Temperature dependence of the Fowler-Nordheim current in metal-oxide-degenerate semiconductor structures[END_REF].

It is worth noting in Figure 2 an increase in recorded current for one voltage sweep direction compared to the other as the voltage gets near the energy barrier (15 V and 10 V for NW2 and NW3). The voltages are applied from zero to the negative maximum and then from zero to the positive maximum. The current is noticeably higher for the latter measurement, indicating that something has happened during the first voltage sweep such as charging of impurities or defects that results in this hysteresis. The hysteresis may be due to traps on the surface or in the bulk that are charged the second time voltage is applied, or it may instead be due to restructuring of the gold due to electromigration [START_REF] Alam | Creating New VLS Silicon Nanowire Contact Geometries by Controlling Catalyst Migration[END_REF].

Influence of nanowire surface oxidation

Different gases can be introduced in the TEM column, allowing us to modify the composition of the nanowire surface in between I-V measurements. To study the effect of oxidation we introduced oxygen after measuring I-V data on oxide-free nanowire NW1, Figure 4. Pressures in the 10 μTorr range were used for each of three in situ oxidation steps, and the last step included resistively annealing the sample to approximately 400 o C. This is expected to enhance the surface oxidation, since the reaction is strongly temperature dependent [START_REF] Seo | Surface Charge Density of Unpassivated and Passivated Metal-Catalyzed Silicon Nanowires[END_REF]. A final oxidation step was carried out at 1 atm. ex situ by removing the sample from the TEM vacuum for 10 minutes. No oxidation layer was visible in the TEM before this ex situ oxidation, while an oxide layer of ~ 2.4 nm was visible afterwards (Figure 4b and Figure S10 ). A linear fit of I-V data of the last two oxidation steps (Table S4) shows an increase in the resistance by a factor of 10 indicating that the oxide layer affects the resistance strongly beyond the minuscule reduction in the diameter of Si from the oxidation. The resistance values for each oxidation step are summarised in Figure 4d.

These curves were fitted with a power law and the exponent of the power law for each step is shown in Figure 4c. This clearly shows a shift from a power law with an exponent of 2, indicating the PF model as discussed above, down to 1.5. After annealing, the exponent goes down to 1. The surface modification removes the non-linearity, showing the effect of the surface on the conductance; annealing leads to linear behaviour. We speculate that this may be due to changes in the traps, perhaps by breaking up the surface monolayer of Au into isolated Au islands, as shown in Figure S10. This result could therefore indicate that the initial non-linearity was caused by a PF trapping effect from the gold monolayer rather than the SCLC trap-free effect, as we have argued above. Oxidation in ambient air will form a depletion layer under the oxidised layer that will eliminate the doping effect of the nanowire, as described by Park et al. [START_REF] Park | Extraction of Doping Concentration and Interface State Density in Silicon Nanowires[END_REF], and the PF trapping effect. Hence, PF trapping by the gold monolayer and formation of a depletion layer by oxidation in ambient can account for the changes in the conductance.

Higher voltages for oxidised nanowires

After the fourth oxidation step, high voltages were applied to NW1. The nanowire was able to survive up to 35 V in vacuum (Figure S11). The I-V measurements show a characteristic avalanche breakdown current with a low dynamic resistance above the threshold voltage, as seen in previous studies of Si-Au-Si connected nanowires [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF]. The avalanche threshold voltages are expected to be above 20 V (Table S5) based on the model discussed by Kallesøe et al. [START_REF] Kallesøe | Situ TEM Creation and Electrical Characterization of Nanowire Devices[END_REF], as shown in Figure S11.

Temperature effect on oxidised nanowires

We systematically studied the temperature dependence of the I-V curves of two nanowires, NW6 and NW7, oxidised in ambient atmosphere and probed ex situ TEM on a thermal stage to study the thermoresistivity of the nanowires and extract the related activation energy. We found the I-V curves to be linear (Figure S12). The Arrhenius plot, Figure S13, of temperature-dependent resistance of ambient oxidised nanowires show an Arrhenius dependence with activation energy Ea of the order 300-350 meV. This is considerably more than the 60 meV expected [START_REF] Zhu | Temperature dependent resistance and cryogenic microwave spectroscopy of Au decorated silicon nanowires[END_REF] for hopping conduction between gold islands. It is also higher than the 60 meV reported for detrapping from Coloumb traps that originate from crystallographic misorientations [START_REF] Acharya | Poole-Frenkel Transport in Gold Catalyzed VLS Grown Silicon Nanowires[END_REF][START_REF] Acharya | What causes Poole-Frenkel transport in VLS grown silicon nanowires?[END_REF]. The high activation energy is similar to that found from deep traps caused by Au within and on the sidewalls of highly p-doped silicon nanowires studied by deep-level and photoinduced current transient spectroscopy [START_REF] Sato | Electronic Level Scheme in Boron-and Phosphorus-Doped Silicon Nanowires[END_REF]. In these nanowires, the electrical conductance was also affected by deep traps from gold in nanowires with a monolayer of gold on the surface, but was more clearly measurable when the surface was oxidised.

Conclusion

We have investigated transport mechanism in individual silicon nanowires (with monolayer Au on the surface) that were grown, electrically connected and modified inside a TEM. In this setup, nanowires can be probed at high temperatures as they are connected between microheaters. In addition to manipulating transport by temperature, we can also introduce gases like oxygen to oxidise the wire surface inside the TEM. The observed I-V curves of nanowires before and after oxidation and at room and high temperature were compared to several possible transport models. No single model can explain all the data, suggesting that conclusive model assignment will require a range of experiments with varied parameters such as radius, doping and temperature. However, from the available data, we observed that electronic transport in wires of different diameter is dissimilar despite the common growth mechanism. The electronic transport in ~50 nm diameter nanowires is nonlinear down to 0.13 V and appears best described by the Poole-Frenkel effect while larger wires (with 100 nm diameter) exhibited Ohmic behaviour at low voltages and nonlinear behaviour above 5V that fits with resistive heating models and also shows the characteristic turning point from the injection-limited Fowler-Nordheim model. We demonstrated a transition from nonlinear to linear I-V characteristics by gradual in situ and ambient oxidation of nanowire surface. TEM images show a modification of the surface structure as oxidation breaks the gold monolayer on the surface into gold islands, thus reducing the conduction on the surface. The increase (by a factor of 10) in the resistance of the nanowire after oxidation could also hint at the formation of oxide traps that lead to a depletion effect. Transition to linear I-V behavior is also achieved by operating the nanowire at high temperatures around 500 o C, and the dominant contribution to transport then comes from intrinsic carriers. For nanowires oxidised in atmosphere, increasing the temperature reveals an activation energy of 300 meV that further hints at formation of deep trap states in oxidised wires.

Our experiments demonstrate that in situ electrical measurements can reveal transitions in nanowire conduction mechanisms that would be challenging tasks for postfabrication, ex situ characterisation tools. With in situ TEM data, we can measure the precise dimensions of the electrically probed nanostructure and combine it with techniques exclusive to TEM such as HRTEM, electron diffraction, EDS and EELS. A comprehensive relation between structure, composition and electronic transport can be established, provided enough data is collected, with measurements at a range of temperatures, diameters and surface structures. Finally, the development of this in situ method to grow and electrically characterise silicon nanowires inside the TEM can help us in understanding the behaviour of other nanowire compositions, potentially including III-V nanowires, heterostructure devices and quantum dot systems. In the future, in addition to in situ heating or surface modification, stimuli like irradiation with light could also be used to perform detailed characterisation of optically active nanowires.

Figure 1 .

 1 Figure 1. Illustration of setup up with (a) two cantilevers with a bridging nanowire, which has been (b) magnified to show different possible sources for non-linear current. Growth is from left to right in the direction of x axis. At the base is a Si-Si contact. At the tip, the contact may also be Si-Si or may include Au as shown in the inset. (c) I-V plots for five nanowires measured at various temperatures. (d)-(e) Energy bands for bulk-limited transport models and (f)-(g) energy barriers for injection-limited transport models that can produce non-linear I-V characteristics, see text.

Figure 2 .

 2 Figure 2. Images of three different types of nanowire connections: (a) small diameter nanowires and large diameter nanowires with (b) Si-Si and (c) Si-Au-Si contact, respectively. The corresponding I-V curves are plotted with the absolute value of the negative voltage and current. The difference of the absolute value of positive and negative current (I+-I-) is also plotted. A linear Ohmic fit up to 3V is illustrated for (b) and (c) by dashed lines. The blue lines in TEM images in (b) and (c) distinguish the nanowires of interest from overlapping out of focus wires. Scale bar is 50 nm.

Figure 3 I

 3 Figure 3 I-V-measurements for nanowires NW1, NW2 and NW3 with different transport models applied. (a) Resistive heating model applied on I-V curves from NW1, NW2 and NW3. (b)-(c) Bulk-limited current models given for nanowires with two different diameters, both with Si-Si contacts. (d)-(e) Injection-limited current models for two kinds of contacts, Si-Si and Si-Au-Si. The scale bar in all TEM images is 50 nm.

Figure 4 -

 4 Figure 4 -Oxidation of nanowire NW1 in four different steps. (a)The I-V curves have been fitted to a power law (I ̴ V a ) and the exponent for the different steps are given in (c) together with the changes in resistance in (d). The TEM image (b) is after ex situ oxidation. Scale bar in (b) is 10 nm.

Acknowledgements

This work was part of the FTP Nano Live project, which was funded by The Danish Council for Independent Research (Case No.10-083797). This work was partly supported by The Danish National Research Foundation's Center for Individual Nanoparticle Functionality, CINF (DNRF54). The work was also supported by DTU Nanolab, DTU Fotonik and the Knut and Alice Wallenberg Foundation.

AUTHOR SUBMITTED MANUSCRIPT -draft

Journal XX (XXXX) XXXXXX

Author et al

Author contributions

O. These authors contributed equally to this work.


Herve Bertin

Yoann Brûlé

Giovanni Magno

Thomas Lopez

Philippe Gogol

Boris Gralak

David Barat

Guillaume Demésy

Beatrice Dagens

PLASMONIC NANOSTRUCTURES ARRAY WITH CORRELATED DISORDER FOR AUGMENTED REALITY

Augmented reality makes life easier for users in different domains like education, industry, and medicine. Head-up displays (HUD), used in the automotive domain, can be seen as one early development of augmented reality systems. HUD consists in reflecting a colored display on a transparent glass plate which indicates driving relevant information to the driver. In order to reduce display consumption and/or to obtain sufficient contrast in case of sunny weather, it is necessary to increase the plate reflectance at image color wavelengths. More precisely, the challenge is to develop a plate with simultaneously high reflectance, high angular tolerance and high transparency, providing a clear reflected picture and a clear view of the landscape behind the plate. Among different technologies, localized plasmonics, based on noble metal nanoparticles (NPs) resonances, enables local modification of colors and versatile HUD plate designs [START_REF] Barnes | Surface plasmon subwavelength optics[END_REF][START_REF] Brûlé | Design of metallic nanoparticles gratings for filtering properties in the visible spectrum[END_REF]. Usually, designs of resonant NPs arrays are performed considering periodic layout, more suitable for current numerical tools. However, disordered arrangement presents several advantages: attenuated light diffraction, possible low cost and large scale fabrication, versatile design… Here we first experimentally show that subwavelength period square lattice NPs arrays present similar reflection and transmission properties to the corresponding disordered ones with the same spatial density, regardless of the resonance wavelength, the polarization (p or s) and the angle of the incident light (Fig. 1). The resonance peaks are tuned by modifying the size of the NPs. The reflectance maxima follow the plasmonic resonance intensity, dependent on the wavelength. The targeted color in this work is amber, corresponding to 590nm wavelength. NPs resonant at 590nm are considered in the following.

Then, by decreasing the NPs spatial density to increase the plate transparency, possible diffraction orders and surface lattice resonances [START_REF] Guo | Geometry dependence of surface lattice resonances in plasmonic nanoparticle arrays[END_REF] of the square lattice reflectance spectrum disappear in the case of the disordered array (Fig. 2 a,b). Finally, a wide range of reflectance/transmittance ratio can be obtained by using NPs disordered spatial arrangement, simultaneously avoiding diffraction effects in the visible range (Fig. 2c). Experimental and numerical results are in excellent agreement [START_REF] Bertin | Correlated disordered plasmonic nanostructures arrays for augmented reality[END_REF]. However, whereas the disorder allows suppressing the diffraction rays, it also may induce light diffusion effect. For this reason, we have considered here correlated disorder, in the sense that the relative positions of the NPs is not fully random. The distance between adjacent NPs is constant (by an error bar lower than a few percent): this design is expected to avoid light diffusion effects [START_REF] Conley | Light Transport and Localization in Two-Dimensional Correlated Disorder[END_REF], and also to ease fabrication.

Two samples of 1 cm² with disordered arrays of 21 and 16 NPs/µm² respectively have been fabricated (Fig. 3) and qualitatively evaluated: no diffusion or diffraction rays appear. Then the sample with the lowest density, corresponding to the best reflectance/transmittance compromise, has been tested in a miniaturized lab HUD bench (Fig. 4). There, the objective is to evaluate the relevance of the design in a realistic situation. Clearly, the reflectance at amber color is significantly increased with respect to uncoated glass, without degrading the quality of the landscape view through the sample. To conclude, these promising results pave the way for HUD systems and could find some innovative applications in the transport industry such as in the automotive or aeronautic sectors for displays, human-machine interfaces, and sensors.

Fig. 1 .

 1 Fig. 1. Fabricated samples: (a) SEM images of the square lattice (left) and correlated disorder (right) NPs arrangements. Backlit photography of the sample with pairs of "Sq" and "Rd" arrays with 200nm (Sq) and 216nm (Rd) average interparticle distances and different ellipses diameters (formatted as "a x b" given in nm). (b) Reflectance and transmittance spectra for Sq and Rd arrays with identical NPs and both polarizations. (c,d) Reflectance and transmittance peaks spectral positions of all arrays and different angles for both polarizations.

Fig. 2 .

 2 Fig. 2. (a,b) Experimental reflectance spectra for different arrays spatial densities (from 8 to 25 NPs/µm²) respectively for Sq and Rd arrays. (c) Reflectance maxima in S polarization and averaged transmittance (for both polarizations on the whole visible spectrum) versus the array density. The best compromise is obtained for the density of 16 NPs/µm².

Fig. 3 .

 3 Fig. 3. From left to right, down: qualitative observation of a landscape through a plate of respectively 21 NPs/µm², null and 16 NPs/µm² array spatial density. Up: photographs of the backlit and illuminated corresponding plates.

Fig. 4 .

 4 Fig. 4. (a) Road image without (left) and through (middle) the plasmonic plate. (right) HUD like experiment with the fabricated plasmonic plate, and (b) color description on color gamut (clear blue square), to be compared with reflected image on glass only (dark blue square), perfect mirror (white circle) and with '590 nm' color (black square). (c) Corresponding reflectance at 590 nm.

This work has been supported by the ANR funded project PLANISSIMO (ANR-12-NANO-0003) and by the french RENATECH network.


Benjamin Leroy

Giovanni Magno

David Barat

Laetitia Pradere

Béatrice Integrated Dagens

Plas

Integrated Plasmonic Nanoantenna Gratings for Large Area Coherent Optical Source

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Integrated Plasmonic Nanoantenna Gratings for Large Area Coherent Optical Source

Benjamin Leroy The emission of coherent light from a large area with a controlled directivity is required for high quality holographic system. In application domains like automotive, such a source needs to be fully planar for compactness and portability. It can be made of discretized sub-sources as long as they remain coherent and with the same directivity. We have considered here an array of connected waveguides covering the surface of a glass substrate. These waveguides spread the laser light out on the whole surface. Discretized plasmonic nanoantennas positioned at specific locations along the waveguides realise then the out-of-plane coherent beam steering.

Directive light emission has been demonstrated in Yagi Uda antenna based integrated structures [START_REF] Curto | Unidirectional Emission of a Quatum Dot Coupled to a Nanoantenna[END_REF][START_REF] Kosako | Directional control of light by a nano-optical Yagi-Uda antenna[END_REF][START_REF] Arango | Plasmonic Antennas Hybridized with Dielectric Waveguides[END_REF]. In all cases, the most part of the far-field radiation is directed toward the higher refractive index medium, with an angle determined by the refractive index contrast. So in these configurations, there is no way to chose the beaming angle, unless by changing the refractive index contrast.

Here, in order to obtain an out-of-plane beaming having a full angle control at visible wavelength, we propose an emitter structure composed of a plasmonic nanoantennas periodic grating coupled to a monomode dielectric Si3N4 waveguide embedded in a homogenous SiO2 medium [START_REF] Février | Giant coupling effect between metal nanoparticle chain and optical waveguide[END_REF][START_REF] Février | Metallic nanoparticle chains on dielectric waveguides: coupled and uncoupled situations compared[END_REF]. The Bragg grating function of each scatterer controls the directivity (direction and divergence) of the beam, whereas the localized plasmonic resonance of nanoantenna monitors the coupling efficiency (Fig. 1). We show that each grating plays the role of a scatterer with full control of the beam shape and emitted power by independent design parameters (Fig. 2): up to 8 emitters can be positioned in series delivering similar emission diagram in shape and intensity. This confirms the feasibility of a large area coherent source by using plasmonic nanoantenna gratings positioned near a dielectric waveguide [START_REF] Leroy | Integrated Nanoantenna Gratings For Planar Holographic Signalisation System[END_REF]. First experimental results validate the approach. Additionally we identify and analyse coupling mechanisms between nanoantenna chains and surface lattice modes, for the first time in a waveguiding excitation configuration.

Fig. 1 ,Fig. 2 ,

 12 Fig. 1, elementary integrated scatterer made of two silver NP chain positioned at each side of the silicon nitride waveguide, and related design parameters (ax, ay, d and D'). Corresponding fabricated device (SEM image) Fig. 2, (left) experimental and numerical far field map of emitted light à 633 nm. (right) Tunability of the waveguide-nanoantenna coupling efficiency by NP size (3values of the nanorod ellipse large diameter ay) for d=300nm.

  1 , Giovanni Magno 1 , David Barat 2 , Laetitia Pradere 2 , Béatrice Dagens 1 1. Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N, F-91120 Palaiseau, France 2. Groupe PSA, Direction Scientifique, Centre technique de Vélizy, route de Gisy, 78140 Vélizy-Villacoublay, France


Loren D Hayes
email: loren-hayes@utc.edu

Leticia Aviles

Eduardo Fernandez-Duque

Maren Huck

Eileen A Lacey

Adriana Maldonado-Chaparro

Miles Matchinske

Neville Pillay

Nancy G Solomon

Carsten Schradin
email: carsten.schradin@iphc.cnrs.fr

Using remote seminars to teach animal behavior

Keywords: FINE, education, remote seminar, animal behavior, COVID-19, teaching, lecturer

We are

GLOSSARY

Credit: Students accumulate "study credits" to finish their studies, or to be allowed to participate in exams. For example, European Credit Transfer (ECTs) and Accumulation System credits, where 1 ECT corresponds to 25-30 hours of work. Diversity: Students and lecturers of different backgrounds, including but not limited to differences in age, gender, sexual orientation, race, ethnicity, culture, religion, geography, disability, socioeconomic status, area of expertise, level of experience, thinking style, native language, or skill set (sensu [START_REF] Swartz | The science and value of diversity: closing the gaps in our understanding of inclusion and diversity[END_REF]. FINE: International Remote Seminar on Frontiers in Social Evolution. A remote seminar that offers live participation in talks of 45 minutes followed by 60 minutes of discussion. Talks occur via Zoom and YouTube and are stored on YouTube where they are available for later viewing and re-viewing: https://www.youtube.com/channel/UClXFO1pLpCTBy7vSwLWH-GA Learning: The acquisition of new understanding, knowledge, skills or attitudes. Learning can be enhanced and facilitated by the teaching approach and philosophy of lecturers. Lecture: Any activity where teaching is done by lecturers, including modules, classes, labs, and practica. Lecturer: Anybody who teaches, including but not restricted to teachers, instructors, and professors. Program: A set of educational activities that lead to an academic degree, e.g., bachelors, honors, masters, doctorate. Remote Seminar: A seminar that is held on any video communication platform. It refers primarily to seminars which store the presented talks permanently on video platforms, making them available for later viewing and re-viewing. Student: A person enrolled at a university to obtain a degree, including Ph.D. students. Teaching: Any instructional effort, including 'front-of-class' teaching (whether remote or live on campus) and more interactive formats (seminars, workshops, labs), as well as student-led, self-directed approaches where the lecturer only acts as a guide or facilitator Teaching activity: Any action by students that facilitates learning, e.g., reading, discussing, note taking, writing a summary or essay, interviewing a scientist. Teaching tool: A resource (here derived from remote seminars) that can be used by lecturers to develop specific teaching activities. Examples include stored videos or already prepared instructional slides. University: Any institution of higher education. 67 68

INTRODUCTION

The abrupt transition to remote learning necessitated by the COVID-19 crisis has created numerous challenges for university lecturers (see Glossary; Bao 2020; Barton 2020; [START_REF] Elsalem | Remote E-exams during Covid-19 pandemic: A cross-sectional study of students' preferences and academic dishonesty in faculties of medical sciences[END_REF][START_REF] Hughes | Teaching animal behavior online: A primer for the pandemic and beyond[END_REF]. At the same time, this transition has produced new and creative educational opportunities, many of which are just beginning to be realized. At a first step, numerous departmental seminar series had been shifted to remote platforms. Notably, increased use of digital platforms to convene research seminars in a wide range of disciplines has revealed the ease with which large, international communities of colleagues can be brought together to share information and resources that readily lend themselves to use in instructional contexts (Botchkarev 2020, Bottanelli et al. 2020[START_REF] Wood | Frontiers in Social Evolution (FINE) Remote Seminar, Spring 2021 announcement[END_REF][START_REF] Zipple | How long-term studies reveal otherwise unhidden phenomena: The Long-term Research Seminar Series[END_REF]; Table 1). Such remote (online) seminars create important opportunities for students to explore established and emerging research in a dynamic, discovery-based format that can be tailored to fit a diverse array of instructional levels, learning objectives, and institutional settings. Ease of international participation by both presenters and audience members promote diversity in research and reduces barriers to access while facilitating new educational and research collaborations.

Here, we illustrate how remote seminars can be used in teaching of animal behavior. Our aims are to (i) demonstrate what teaching tools derived from remote seminars are already available to lecturers in animal behavior and (ii) inform organizers of remote seminars what teaching tools they can make available to lecturers. As an example, we describe a series of teaching activities that we have developed in concert with the International Remote Seminar on Frontiers in Social Evolution (FINE), which began in September 2020 [START_REF] Wood | Frontiers in Social Evolution (FINE) Remote Seminar, Spring 2021 announcement[END_REF]. Originally conceived as a forum for sharing research, it quickly became apparent that the FINE and other remote seminars offer critical learning opportunities for students. To capitalize on these opportunities and to share these resources more broadly, we outline multiple ways in which students can engage with remote seminars to increase understanding of key behavioral concepts, improve skills associated with critical evaluation of behavioral research, and promote clear written and verbal communication regarding primary research findings. For this -as for any teaching effort -it is important to first define learning outcomes, describe the proposed tools, and illustrate how these tools can be integrated into the classroom. As terminology in higher education differs among countries and institutions, we provide a glossary of the terms we use (Glossary).

LEARNING OUTCOMES

Students at all levels may benefit from remote seminars in three domains of cognitive (learningknowledge), psychomotor (skills) and affective (attitudes and values) learning (sensu Bloom et al. 1956). The level at which the suggested teaching activities may be used to facilitate these learning outcomes should be contingent upon students' prior knowledge and the goals and scope of the learning experience (Cannon & Feinstein 2005).

Knowledge

This domain considers the question "What do we want students to know?". It encompasses facts, terminology, principles, models, and theories [START_REF] Vaughan | Identifying course goals: domains and levels of learning[END_REF]. Remote seminars and their associated teaching tools may contribute to these various areas of knowledge. For example, several remote seminars (Table 1) addressed concepts in animal behavior, ecology and evolution, as well as the process of doing science using natural history observations, experimental manipulations in the field or laboratory, comparative approaches, and analytic models or simulations. Remote seminars offer students access to more international knowledge from primary sources (i.e., scientists and their students), instead of getting this knowledge via secondary or tertiary resources, such as textbooks. Depending on course-specific goals, lecturers could emphasize these topics in lectures and inquiry-based activities (e.g., laboratory experiments), as well as engage students in discussion about these topics.

Skills

This domain addresses the question "What do we want students to be able to do?". It encompasses techniques for critical thinking, problem solving, and communication (Conklin 2005). Remote seminars give students the opportunity to observe a range of scientific methodologies in action and to identify the questions, hypotheses and experimental design used by the presenter, as well as to practice interpreting graphs and tables. In lectures, students can be directed to work in teams to evaluate the science being presented and perhaps propose alternative hypotheses or experimental designs. By participating in a discussion period with an invited speaker, students can develop skills for formulating and asking questions and learn about the skills (including personal and administrative) the researcher needed to establish and maintain the project. Additional activities may require students to communicate with each other, or to prepare a presentation based on a given teaching tool, which would further enhance development of communication skills.

Attitude

This domain is concerned with affective learning, namely how to enrich student attitudes and values, in this case towards science. In the context of remote seminar tools, this domain addresses the questions: "What do we, as researchers, want students to think or care about?" and "How do we as researchers engage students in developing their own attitudes and values as future professionals?" It includes developing awareness of ethics, morals, and the practice of these values in one's professional and everyday life [START_REF] Maclean | The human factor in learning design, research, policy, and practice[END_REF]. Remote seminars provide examples of real-world scientists communicating research about which they are passionate. These seminars should also inspire an appreciation for evidence-based arguments while illustrating the different ways that scientific problems can be approached (e.g., field and comparative research, modeling). Additionally, such seminars exemplify the importance of science communication, typically to peers, but may also inspire the need to communicate science to the general public. Finally, by involving international researchers of different backgrounds, accents, and experiences and showcasing research done around the world, remote seminars promote diversity, stimulate discussion on the ethics of working in different countries, and highlight the scientific and cultural advantages of building teams of collaborators with diverse backgrounds.

ETH-21-0135 7

Networking

In addition to the core learning domains, using teaching tools derived from remote seminars in the classroom (for details see below) will allow students to expand on other professional skills that will aid their career advancement (Turnbull & Gotian 2020). Remote seminars provide a safe environment where students at different levels, especially those in early career stages, can build their confidence by participating in discussions and interactions with peers and near-peers (e.g., group discussions involving undergraduate and graduate students). Further, attending live seminars gives students networking opportunities, particularly when engaging in the discussion with speakers. Such discussions allow students to practice two important skills needed to develop and maintain a professional network: how to be an active listener and how to ask questions. Mastering these skills provides the foundation for honest and enduring interactions with colleagues that can result in productive collaborative relationships.

TEACHING TOOLS EMERGING FROM REMOTE SEMINARS

Here, we describe how remote seminars can be used for teaching and how teaching tools similar to those produced by FINE can be used to enhance student learning experiences (Table 2). Details of tools developed by the FINE community are described in Box 1.

Remote seminar attendance

Historically, many universities have treated participation in seminars or conferences similarly to enrolling in a course. For example, Ph.D. students in many countries have to obtain credit points during their studies; participating in a seminar can contribute to this. However, it may be difficult for students to prove that they have participated in a remote seminar. Organizers of remote seminars can provide certificates of attendance if they can verify that students participated. This is time-consuming for seminars with large audiences and can be challenging for the seminar organizer while hosting a speaker and ensuring that the seminar progresses without technological issues or interruptions. Another option for verifying participation is to ask students to submit written summaries of presentation within 24 hours of a seminar (Supplementary Material S1). Submitted summaries will provide university officials information they can use to decide how many credit points can be given. This tool could be further developed by local lecturers who could then give more credit to students. For example, lecturers could give their students detailed instructions on what kind of syntheses they have to submit after each seminar to qualify for study credit points.

Relevant articles

Reading and discussing the primary literature can have numerous intellectual and personal benefits for students [START_REF] Kozeracki | An intensive primary-literature-based teaching program directly benefits undergraduate science majors and facilitates their transition to doctoral programs[END_REF]. Reading articles related to a seminar prior to viewing the presentation can improve general understanding of a speaker's research theme, reducing energy spent during the seminar to understand basic terms and concepts while helping to generate more informed questions. These benefits are amplified when members of research groups or journal clubs discuss recommended readings together, prior to, or after seminars [START_REF] Glazer | Journal clubs -a successful vehicle to science literacy[END_REF]; this can be particularly beneficial when reading groups consist of individuals from research groups from around the world. Remote seminar organizers can facilitate these activities by asking speakers to provide bibliographical information for several relevant articles and making this information available to seminar participants before the seminar, such that students and lecturers can prepare themselves.

Teaching slides

Presentations in seminars, including those online, are typically 45-60 minutes long, which limits their use in the classroom. Furthermore, extracting the take home messages from long seminars may require considerable effort by the lecturer. To facilitate the use of remote seminar presentations in the classroom, presenters can prepare sets of teaching slides that are made available to the scientific community. Such teaching slides will contribute to disseminating the work of presenters to future generations of scientists. Presenters could be encouraged to record themselves explaining the content of the slides. Together with a photo of the researcher on the title slide, this brings the international expert directly into the classroom, making it a more personalized experience for students. The audio portion can be muted, or deleted, from the presentation if the lecturer prefers. Providing students access to slides and audio recordings will increase accessibility to students with limited ability to attend seminars and promote the review of relevant course information outside of class. Providing captions improves accessibility to students with hearing impairments or other challenges to auditory processing of information.

Recorded seminars

It is common practice that remote seminars are recorded and stored on video-platforms [START_REF] Zipple | How long-term studies reveal otherwise unhidden phenomena: The Long-term Research Seminar Series[END_REF]. This enables lecturers to show seminars (or parts of them) during diverse class times, or to require viewing them as an assignment to be completed at home. Several teaching activities can then be associated with these recorded seminars, including student discussions, written summaries, and development of new activities (e.g., grant proposals, interviews with speakers). Numerous seminars are live streamed and freely accessible on specific YouTube channels (Table 1) and other video platforms (Bottanelli et al. 2020). Recorded seminars can be used to generate student-led discussions during lecture periods. Lecturers can invite remote seminar speakers to join the discussion after students have watched the seminar. Students can prepare for a discussion with the remote seminar speaker by writing a summary and preparing a few questions about a related article. They can ask the speaker questions about the seminar, the speaker's career path, and related academic issues. The benefits are numerous; students improve their understanding of research, learn how to interact with international scientists, build confidence, and develop networking skills (Box 2).

SCIENCE COMMUNICATION

The COVID-19 pandemic has highlighted the well-known importance of science communication skills [START_REF] Kelp | Scaffolded curriculum for developing Science Communication skills in Life Science undergraduates[END_REF], thereby underscoring calls to integrate science communication more fundamentally into science education and training (Dahm et al., 2019). Various universities either encourage or require students to gain work-based experience in communicating scientific ideas. For example, the University of Derby, UK, runs a final year undergraduate module taken by students in programs ranging from Biology and Zoology to Human Biology and Forensic Sciences. As part of the course, students have to create a ~ 3 minute public facing video. Students choose the topic, as well as the target audience. Similar assignments could be included in a variety of undergraduate and graduate animal behavior courses. For example, engaging deeply with the content of a seminar will increase understanding of principles of behavioral ecology. This yields clear benefits to not only the recipients but also the creators of science communications or outreach activities (Clark et al., 2016). Organizers of remote seminars could publish high quality videos of this type on their homepages and YouTube channels (for an example see https://www.youtube.com/watch?v=iKKHQwT-cuQ). The prospect of creating a video that will be publicly available and have the "stamp of approval" of established scientists could act as a powerful incentive to produce coursework of the highest standard.

ACCESSIBILITY & DIVERSITY

The expansion of remote seminars and other remote means of scientific discussion (e.g., virtual conferences) during the COVID-19 pandemic has increased accessibility of research to students and lecturers from around the world [START_REF] Skiles | Beyond the carbon footprint: Virtual conferences increase diversity, equity, and inclusion[END_REF][START_REF] Estien | Virtual Scientific Conferences: Benefits and How to Support Underrepresented Students[END_REF]. Accordingly, remote seminars reach a diverse audience and have the potential to improve the diversity of the animal behavior community (Lee 2020; Tang-Martinez 2020; [START_REF] Hughes | Teaching animal behavior online: A primer for the pandemic and beyond[END_REF]. For example, the FINE community consists of > 300 individuals, including students and lecturers at various career stages, from > 25 countries spread over 5 continents. The FINE organizers have shared teaching tools with their community (Box 1). To capitalize upon this diversity, organizers of all remote seminars should share teaching tools with their community. Organizers of remote seminar series can also take additional steps to increase accessibility and diversity. Advertising remote seminars across multiple platforms, including email distribution lists and various forms of social media will reach a diverse audience. Using multiple forms of livestreaming (e.g., FINE seminar is livestreamed on Zoom and YouTube) makes the seminars accessible to a broad audience, including students and lecturers with conflicting schedules and non-scientists, alike. Recording the seminars to freely accessible video platforms increases access to students and lecturers with restrictions (e.g., limited computer access, some learning disabilities). Finally, organizers of remote seminar series should invite speakers from institutions that serve individuals from members of under-represented minority groups.

RECOMMENDATIONS (1) Use remote seminars and teaching tools in lectures.

A key feature of many remote seminars is that they can be adapted to suit the needs of a wide range of courses, ranging from introductory to advanced undergraduate and graduate classes. This is true for many different countries (Supplementary Material S3). Lecturers can choose teaching tools and teaching activities based on numerous factors including specific course learning outcomes, method of lecture (e.g., in person, asynchronous or synchronous online), class size, course level (e.g., undergraduate, graduate), format (e.g., lecture, discussion), and students' access to resources. As such, remote seminars offer quality and flexibility for learning in a changing world. For example, students in introductory courses can be introduced to key concepts and hypotheses using teaching slides provided by remote seminar speakers. These activities can be followed by class discussion or preparation of written summaries of key points. Students in upper-level courses (see Box 2 for a detailed example the implementation of FINE teaching tools) can explore topics in greater depth by watching an entire remote seminar. Associated activities can include visiting a speaker's website, writing grant proposals, or summarizing additional papers by the speaker. We encourage lecturers to create the combination of activities that best suits their goals, including developing exercises of their own that stem from remote seminar presentations.

(2) Use remote seminars in institutional seminar series. At institutions around the world, inperson seminar series have been used as an instrument to disseminate scientific advances. However, prohibitive travel costs and lack of funds limit the ability of many institutions to host national and international seminar speakers. Remote seminars offer a cost-effective (and environmentally friendly) way to diversify seminar series and opportunities. Incorporating remote seminars into institutional seminar series would benefit students and lecturers at the host institution, as well as speakers who are unable to travel for personal, financial, and professional reasons.

(3) Use remote seminars to promote international collaborations. Remote seminars can connect students and lecturers across states (or provinces) and countries, promoting national and international lecturer-student and student-student networks. For example, lecturers can facilitate journal clubs involving multiple research groups, members of which discuss the relevant articles prior to watching remote seminars. These joint journal clubs could be informal, or part of formal student training programs, such as those that support international student research (e.g., U.S. National Science Foundation International Research Experiences for Students). As is the case for FINE, organizers of remote seminar series could arrange virtual, individual meetings with speakers and members of their research groups before and after seminars. Likewise, we recommend that organizers of remote seminar series allow time for extended discussion immediately following the seminar. Our experience is that these extended discussions allow a diversity of attendees -including students -to participate while providing important feedback to speakers. Finally, we encourage lecturers to work with their respective universities to encourage cross-listed courses that allow students from multiple institutions to engage in remote seminars. Ultimately, these ways of connecting students and lecturers could promote international collaboration and provide novel ways of teaching and informing animal behavior research.

CONCLUSIONS

Remote seminars give international lecturers and students free access to leading scientists in their discipline. When these seminars are stored on video-platforms, this resource is available indefinitely. Students that previously had limited, or no access, to international conferences can now have weekly access to international experts. Using remote seminars in teaching can be beneficial to students, particularly when presenters join discussions. Such interactions can humanize scientists, broadening the impact of their science and increasing student interest in scientific endeavors and careers. Given their educational value, we think it will be beneficial if such collaborative international remote seminars persist after most universities return to live instruction of students. We encourage organizers and lecturers to think creatively as to how to incorporate remote seminars in classes, discussion groups, and university seminar series. Doing so will increase access of cutting-edge science and researchers to a wide audience and promote a broader participation in scientific endeavor. ETHICAL STATEMENT Ethics approval was not required for this research.

CONFLICT OF INTEREST

The authors declare no conflict of interest. & Feinstein, A.H. (2005). Bloom beyond Bloom: Using the revised taxonomy to develop experiential learning strategies. In: Developments in Business Simulation and Experiential Learning: Proceedings of the Annual ABSEL conference 32, Orlando, FL. Clark, G., Russell, J., Enyeart, P., Gracia, B., Wessel, A., Jarmoskaite, I., . . . Roux, S. ( 2016). Science educational outreach programs that benefit students and scientists. PLOS Biology, 14 (2): e1002368. https://doi.org/10.1371/journal.pbio.1002368 Conklin, J., 2005. A taxonomy for learning, teaching, and assessing: A revision of Bloom's taxonomy of educational objectives complete edition (book review). Educational Horizons 83, 154-159. Dahm, R., Byrne, J., & Wride, M. A. (2019). Interdisciplinary communication needs to become a core scientific skill. BioEssays, 41(9): e1900101. https://doi.org/10.1002/bies.201900101

BOX 1. FINE teaching tools

Teaching slides: FINE presenters are invited to submit up to two sets of teaching slides, each consisting of a title slide, three slides with results and figures, and a conclusion slide (Supplementary Material S2 for instructions to FINE presenters). These slides are most often created in Powerpoint which allows the lecturers to modify them to their specific teaching needs. While the level of complexity of slides is determined by the FINE presenter, lecturers can still adjust them for teaching students of different levels. FINE presenters are encouraged to record themselves explaining the content of the slides. FINE teaching slides are available for free download on the FINE homepage https://www.socialevolutionseminar.com/portfolio-3/project-two-f6cnw and sometimes on the homepages of the individual presenters. Additionally, many FINE teaching slides are available on ResearchGate and can be accessed from the project "FINE teaching slides for social evolution" (https://www.researchgate.net/project/FINE-Teaching-Slides-for-Social-Evolution). By following this project, lecturers will be notified when new slides become available.

Relevant articles:

The FINE organizers request that speakers provide a summary and bibliographical information for three articles related to their seminar. This reading list is then sent to the FINE community before the seminar and is made available to the general public on the FINE homepage (https://www.socialevolutionseminar.com/portfolio-3/project-two-f6cnw).

Remote seminar attendance:

To get a certificate of attendance, the requirement for students is to submit a minimum of three key-points from each talk in a written summary (PDF). Interestingly, students typically submitted much longer and more detailed summaries, indicating their commitment and learning achievements. To verify attendance, organizers did not mark the summaries but only registered their submission.

Recorded seminars: Multiple authors of this paper have already invited FINE speakers to engage with students taking their undergraduate behavior courses (detailed example in Box 2).

BOX 2. Using FINE teaching tools in a behavioral ecology course

In 2021, the lead author (Hayes) used the FINE seminar to promote inquiry-based learning and discussion by 3 rd and 4 th year undergraduate and Master's students who were taking his remote, behavioral ecology course. During the academic term, the students engaged with ten recorded FINE seminars on the FINE YouTube page. Student engagement involved multiple steps (Figure 1). First, the students wrote 200-word summaries and three questions (emphasizing Tinbergen's 4 questions; Tinbergen 1963) about an article provided by the FINE speaker in a journal. Students then watched a recorded seminar together during the first hour of a three-hour class session. Next, the students discussed the seminar topic. For eight out of ten lectures, the speaker joined the discussion via zoom for 45-60 minutes, answering questions about the science and process, as well as their career path. This activity not only promoted inquiry-based learning, but also developed student confidence and ability to interact with leading scientists. To facilitate an inclusive discussion, Hayes moderated the session, calling on students who had a question. If speakers did not join the discussion (two of the 10 lectures), students watched 15-20 minutes of the recorded discussion among FINE participants following the seminar, after which they engaged in discussion with Hayes. After watching the seminar, the students added two layers to their summaries -(i) 2-3 themes of the seminar, written for a non-scientist and (ii) final thoughts and outstanding questions. Altogether, the summaries for each FINE seminar were one-page in length, requiring that students write succinctly. At the end of the academic term, the students wrote a synopsis of the FINE seminars, an activity that emphasized students' abilities to synthesize information. Instructions to students taking Hayes' course are posted at the FINE website (https://www.socialevolutionseminar.com/portfolio-3/project-four-2lsaj).

Student feedback played an important role in the process. In response to verbal student feedback, Hayes changed the organization of the three-hour session. Subsequently, students first discussed a relevant article, preparing them for the seminar. The students then watched the seminar after which they engaged in discussion with the speaker or Hayes. We encourage such flexibility; responding to student suggestions improved the learning process in this class.

  Bao, W. (2020). COVID-19 and online teaching in higher education: A case study of Peking University. Human Behavior and Emerging Technologies, 2, 113-115. https://publons.com/publon/10.1002/hbe2.191 Barton, D. C. (2020). Impacts of the COVID-19 pandemic on field instruction and remote teaching alternatives: Results from a survey of instructors. Ecology and Evolution, 10, 12499-12507. https://doi.org/10.1002/ece3.6628 Bloom, B.S., Engelhart, M.D., Furst, E.J., Hill, W.H.., & Krathwohl, D.R. (1956). Taxonomy of Educational Objectives: The Classification of Educational Goals, Handbook 1: Cognitive Domain. New York: McKay. Botchkarev, V. (2020, March 30). Online science seminars you can enjoy from home. Retrieved from https://www.ascb.org/careers/online-science-seminars-you-can-enjoy-from-home/ Bottanelli, F., Cadot, B., Campelo, F., Curran, S., Davidson, P.D., Dey, G., Raote, I., Straube, A., & Swaffer, M.P. (2020). Science during lockdown -from virtual seminars to sustainable online communities. Journal of Cell Science 133 (15): jcs249607. https://doi.org/10.1242/jcs.249607 Cannon, H.M.

FIGURE

  FIGURE 1. Flow of activities used in Hayes'Behavioral Ecology course for 3 rd and 4 th year undergraduates and Masters' students.

TABLE 1 .

 1 Examples of remote seminar series and other video channels related to studies in animal behavior that emerged during the COVID-19 pandemic. Series are listed in the order of the launching of its first seminar.

	Full name	Platforms	First seminar	Continuation
	Evolution & Ecology	YouTube / Slack	15 April 2020	At least until 2021
	Seminars (EvoEcoSeminars)
	Long-Term Animal Research	YouTube	12 May 2020	Ongoing
	Seminar Series
	International Remote	Zoom / YouTube 1 September 2020 Ongoing
	Seminar on Frontiers in
	Social Evolution (FINE)
	Virtual Seminar on the	unknown	September 2020	Ongoing
	Economics of Risky Health	(not all seminars
	Behaviors (VERB)	are recorded)
	Animal Behavior Society	YouTube	8 October 2020	Ongoing
	World Wide Neuro	unknown	unknown	Ongoing

TABLE 2 .

 2 Different teaching tools and how remote seminar organizers can make them available for lecturers, who then develop different teaching activities.

	Teaching tool	Action by organizer of	Examples of teaching	How to access the tool
		remote seminar	activity by lecturer
	Online seminar	Provide certificate of	Students sign up and
	attendance	participation upon request	participate in remote
		and attendance	seminar, receive credit.

TABLE 1 .

 1 Examples of remote seminar series and other video channels related to studies in animal behavior that emerged during the COVID-19 pandemic. Series are listed in the order of the launching of its first seminar.

	Full name	Platforms	First seminar	Continuation
	Evolution & Ecology	YouTube / Slack	15 April 2020	At least until 2021
	Seminars (EvoEcoSeminars)
	Long-Term Animal Research	YouTube	12 May 2020	Ongoing
	Seminar Series
	International Remote	Zoom / YouTube 1 September 2020 Ongoing
	Seminar on Frontiers in
	Social Evolution (FINE)
	Virtual Seminar on the	unknown	September 2020	Ongoing
	Economics of Risky Health	(not all seminars
	Behaviors (VERB)	are recorded)
	Animal Behavior Society	YouTube	8 October 2020	Ongoing
	World Wide Neuro	unknown	unknown	Ongoing

Supplementary Material S1.

Relevant articles Request that presenters provide bibliographical information for 2-3 relevant articles.

Students read and discuss articles, write summaries.

Available for free download on homepage 1 YouTube page of FINE 3 1 https://www.socialevolutionseminar.com/portfolio-3/project-two-f6cnw 2 https://www.researchgate.net/project/FINE-Teaching-Slides-for-Social-Evolution 3 https://www.youtube.com/channel/UClXFO1pLpCTBy7vSwLWH-GA Figure 1


Simon Gabay

Barbara Topalov

Caroline Corbières

Lucie Rondeau Du Noyer

Béatrice Joyeux-Prunel

Laurent Romary

Automating Artl@s -extracting data from exhibition catalogues

Catalogues, which have been published for centuries, are an extremely precious resource for scholars. Using the Artl@s database as an example, where exhibition catalogues are transformed into a georeferenced database, we question the possibility of an (almost) automatic transformation of pdfs into semantically annotated data. To do so, we present and analyse the graphic organisation of exhibition catalogues, before exploring a possible modeling into TEI (involving possible enhancement of the guidelines).

Databases for art history usually focus on images, and are primarily made by or for museums to display collections (or inventories). 1 Other databases do not focus on the work of art itself, but on a corpus about the work of artsuch as databases used for provenance research 2 or by collectors monitoring the market 3 . The BasArt database of the Artl@s project 4 belongs to the second category as it aims at recording exhibitions all over the world since the invention of exhibition catalogues in the 17th century (Paris, Salon de l'Académie, 1673) 5 . BasArt is essential for art history, not only because it makes available one of the most widely used sources in the discipline, at a global scale and over several centuries, but also because it makes it possible to globalise the horizons 1 of research and to move on to unusual quantitative, spatial, and transnational analyses, without specific knowledge in digital technologies [START_REF] Joyeux-Prunel | Exhibition Catalogues in the Globalization of Art. A Source for Social and Spatial Art History[END_REF].

If data has long been entered manually, by simply copying the content that in the exhibition catalogues describes the works exhibited, we are now designing a new workflow, based on GROBID dictionaries technology [START_REF] Khemakhem | Standard-based Lexical Models for Automatically Structured Dictionaries[END_REF], to semi-automate the task, that is to say to retrieve the content from pdf digitisation of the catalogues, describe it semantically, in order to transform the XML-TEI output of this new workflow into the structured BasArt postGIS database. As our database is structured to deal with catalogues from very different periods of time, and from very diverse locations and languages, we intend to take advantage of the tasks involved in designing a semi-automated retrieving chain -in particular, the description necessary to train recognition algorithms -, to produce research on the history of the form of exhibition catalogues over time and space, and according to the language. The project's ambition is also to enable broader developments that will be useful for other projects dealing with comparable resources and corpora -such as auction catalogues, collection directories, or catalogues raisonnés.

Exhibition catalogues

In order to semantically describe catalogues, we need to analyse their form. This form has a history, which meets the history of the inventory, whose description is a challenge for anyone who wishes to model their structure, but also try to generalise this modeling to any type of similar documents. The inventorium (inventory) can be considered as an early form and the origin of the catalogue. This list of a set of objects forming a collection was originally built by recording collection items in the very order in which they were stored or displayed [START_REF] Barbier | De l'argile au nuage : une archéologie des catalogues IIe millénaire av. J.-C.-XXIe siècle[END_REF]. That is why in France, as early as the Middle Ages, inventories were primarily used to associate a given object to the place where it was preserved. The inventory is first and foremost a practical tool: it is meant to find and identify an object. Inventories also have a scientific/epistemic interest insofar as the classification of objects echoes the classifications of the natural sciences, especially in the case of curiosities cabinets [START_REF] Findlen | Possessing nature : museums, collecting, and scientific culture in early modern Italy[END_REF]. The practice of classifying allows comparison: "Unlike the inventory, the catalogue organises a set of data and arranges them by object, so as to make them comparable with each other." (Recht 1996, p. 23).

With the advent of printing, and the ability to publish inventories for a wider audience, the form of the inventory became semi-industrialised for a few particular types: the catalogues raisonnés of an artist's work, the inventory of a private collection or a museum, the dealer's catalogue, the auction catalogue, the exhibition catalogue. It is with this type of printed data that we believe we can develop a semi-automated pipeline for content retrieval. This process begins with the example of exhibition catalogues.

Generally the content of an exhibition catalogue is quite regular : informa- tion about the event exhibition, its title, date, supposed location, its organisers; a list of the exhibitors -first and last name, sometimes completed by biographical detail, a year and place of birth and an address. Most exhibition catalogues complete these lists of artists with a list, for each exhibitor, of the works exhibited (Joyeux-Prunel and Marcel 2015). Whereas this content is not always represented in the same way in the book-catalogue, it is actually organised according to a limited number of possibilities.

A Stable Layout, Over Time and Place

In the documentation we have gathered (c. 1000 catalogues since the 18 th c., mainly from Western countries), the most recurrent format displays the following information: name of the artist (here, highlighted in red), information about the artist (blue) and a list of the works exhibited (yellow) with potentially additional information (green).

Type 1

Salons, yearly municipal exhibitions and academy exhibitions which were held regularly since the 18th century, usually published catalogues with a very stable layout over time: Figure 8: Tentoonstelling van schilder-en andere werken…, 1852, p.12.

Type 2

A secondary structure coexists with the latter one -a structure that first presents the number and the title of the work, followed by the name of its author. The order is relatively opposite to that described above. This second type of layout, following the exhibition order, has been used for the Exhibition of the Royal Academy in London since 1780, but it can be found in other countries (e.g. Canada). It has been extremely stable over time too. We assume for the moment that these two types may have corresponded to different areas of cultural influence -on the one hand the influence of the Parisian Salon catalogue model, on the other that of a more Anglo-Saxon model. It is likely that another factor explaining these differences is simply that catalogues by work order assume a more commercial character, where it is the work for sale that is presented, and not the artist. This hypothesis is supported by the presence of Type 2 in many gallery catalogues in the early 20 th c.

Beyond exhibition catalogues

According to the two types presented supra, entries can be grouped under superentries, which potentially transmit general properties to entries that they include such as the location of the work in the exhibition (gallery 1, red wing…), or more importantly artistic forms (paintings, sculpture, architecture…). These two types can be found in similar documents, the structure of which is very similar to exhibition catalogues: bibliographies [START_REF] Lindemann | Retrodigitizing and Automatically Structuring a Large Bibliography Collection[END_REF], dictionaries [START_REF] Khemakhem | Enhancing Usability for Automatically Structuring Digitised Dictionaries[END_REF], auction catalogues [START_REF] Gabay | Selling autograph manuscripts in 19th c. Paris: digitising the Revue des Autographes[END_REF], and phone directories [START_REF] Khemakhem | Fueling Time Machine: Information Extraction from Retro-Digitised Address Directories[END_REF]. Such data has been recently identified as "encyclopedic-like" (Khemakhem, Romary, et al. 2018), i.e. entry-based data for which a dedicated retrieval tool has been developed: GROBID dictionaries (Khemakhem 2020). Thanks to the latter, PDF files are automatically structured and annotated in XML-TEI files, which is used as a pivot format to ease encoding refinements via regexes.

The current TEI guidelines6 propose elements allowing research to encode various kinds of lists (<list>, <listPerson>, <listPlaces>, <listObject>…) and their content (<item>, <person>, <place>, <object>…). However, some scholars have noted that encoding a catalogue as a "mere list" was not sufficient if some of its entries feature analytical or descriptive content [START_REF] Nelson | Curating Object-Oriented Collections Using the TEI[END_REF]. Therefore, following the work on dictionaries with TEI-lex 0 (Romary and Tasovac 2018) on the <entry> element, we would like to propose to the TEI Consortium the creation of a <catalogueEntry> element. The behaviour of this TEI markup would be similar to <entry>, transforming <form> and <sense> elements into <catalogueDesc> and <catalogueItem>. A possible encoding would therefore be the one presented infra.

The stakes of this type of classification are both to allow a clearer description of the content, and the possibility of spreadsheet-type retrievals, where the dependencies of a sub-entry on its entry would be maintained (in particular in the repetition of the entry for each line of the sub-entry in the case of an export in csv). This type of processing is ideal for a pivot to databases, more easily handled by users interested in quantitative and cartographic visualisation as is the case for the Artl@s project.

Figure 1 :

 1 Figure 1: Catalogue de l'exposition annuelle du musée de Rouen, 1860, p. 19.

Figure 2 :

 2 Figure 2: Catalogue de l'exposition… de Rouen, 1853, p. 4.

Figure 3 :

 3 Figure 3: Catalogue de l'exposition… de Rouen, 1862, p. 26.

Figure 4 :

 4 Figure 4: Catalogue… exposés à Nancy, 1843, p. 3.

Figure 5 :

 5 Figure 5: Société des artistes indépendants, 1921, p. 17.

Figure 6 :

 6 Figure 6: Esposizione Inter-nazionale… di Venezia, 1910.Figure 7: Bienal de São Paulo, 1951, p. 54.

Figure 7 :

 7 Figure 6: Esposizione Inter-nazionale… di Venezia, 1910.Figure 7: Bienal de São Paulo, 1951, p. 54.

Figure 9 :

 9 Figure 9: The Exhibition of the Royal Academy, 1785, p. 1.

Figure 10 :

 10 Figure 10: The Exhibition of the Royal Academy, 1831, p. 6.

Figure 11 :

 11 Figure 11: The Exhibition of the Royal Academy, 1907, p. 8.

Figure 12 :

 12 Figure 12: The Exhibition of the Royal Academy, 1975, p. 10.

Figure 13 :

 13 Figure 13: Type 1 Figure 14: Type 2

Figure 15 :

 15 Figure 15: Annuaire-Almanach de l'industrie, 1901, p. 2883 compared to the Catalogue de l'exposition annuelle du musée de Rouen, 1860, p. 19.

Figure 16 :Figure 17 :

 1617 Figure 16: Catalogue de feu M. de Bruyères Chalabre,1833, p. 102 Figure 17: Annuaire des imprimeurs et des libraires, 1841, p. 135

Figure 18 :

 18 Figure 18: TEI encoding of a catalogue entry.

http://mandragore.bnf.fr/html/accueil.html

For instance http://www.getty.edu/research/tools/provenance/search.html or https: //ventesdantiques.inha.fr

https://fr.artprice.com/

https://artlas.huma-num.fr

According to[START_REF] Guiffrey | Collection des livrets des anciennes expositions depuis 1673 jusqu'en 1800. 42[END_REF]

https://tei-c.org/guidelines

Data and code

The ODD, the specification and an example can be found at the following address: https://github.com/katabase/Catalogues.