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Cyan

Cyan   is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue.

In the subtractive color system, or CMYK color model, which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta and yellow. In the additive color system, or RGB color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red; it can be made by the removal of red from white. Mixing red light and cyan light at the right intensity will make white light.

Shades and variations
Different shades of cyan can vary in terms of hue, chroma (also known as saturation, intensity, or colorfulness), or lightness (or value, tone, or brightness), or any combination of these characteristics. Differences in value can also be referred to as tints and shades, with a tint being a cyan mixed with white, and a shade being mixed with black.

Color nomenclature is subjective. Many shades of cyan with a bluish hue are called blue. Similarly, those with a greenish hue are referred to as green. A cyan with a dark shade is commonly known as teal. A teal blue shade leans toward the blue end of the spectrum. Variations of teal with a greener tint are commonly referred to as teal green.

Turquoise, reminiscent of the stone with the same name, is a shade in the green spectrum of cyan hues. Celeste is a lightly tinted cyan that represents the color a clear sky. Other colors in the cyan color range are electric blue, aquamarine, and others described as blue-green.

History
Cyan boasts a rich and diverse history, holding cultural significance for millennia. In ancient civilizations, turquoise, valued for its aesthetic appeal, served as a highly regarded precious gem. Turquoise comes in a variety of shades from green to blue, but cyan hues are particularly prevalent. Approximately 3,700 years ago, an intricately crafted dragon-shaped treasure made from over 2,000 pieces of turquoise and jade was created. This artifact is widely recognized as the oldest Chinese dragon totem by many Chinese scholars.

Turquoise jewelry also held significant importance among the Aztecs, who often featured this precious gemstone in vibrant frescoes for both symbolic and decorative purposes. The Aztecs revered turquoise, associating its color with the heavens and sacredness. Additionally, ancient Egyptians interpreted cyan hues as representing faith and truth, while Tibetans viewed them as a symbol of infinity.

After earlier uses in various contexts, cyan hues found increased use in diverse cultures due to their appealing aesthetic qualities in religious structures and art pieces. For example, the prominent dome of the Goharshad Mosque in Iran, built in 1418, showcases this trend. Additionally, Jacopo da Pontormo's use of a teal shade for Mary's robe in the 1528 painting Carmignano Visitation demonstrates the allure for these hues. During the 16th century, speakers of the English language began using the term turquoise to describe the cyan color of objects that resembled the color of the stone.

In the 1870s, the French sculptor Frédéric Bartholdi began the construction of what would later become the Statue of Liberty. Over time, exposure to the elements caused the copper structure to develop its distinctive patina, now recognized as iconic cyan. Following this, there was a significant advancement in the use of cyan during the late 19th and early 20th centuries.

Impressionist artists, such as Claude Monet in his renowned Water Lilies, effectively incorporated cyan hues into their works. Deviating from traditional interpretations of local color under neutral lighting conditions, the focus of artists was on accurately depicting perceived color and the influence of light on altering object hues. Specifically, daylight plays a significant role in shifting the perceived color of objects toward cyan hues. In 1917, the color term teal was introduced to describe deeper shades of cyan.

In the late 19th century, while traditional nomenclature of red, yellow, and blue persisted, the printing industry initiated a shift towards utilizing magenta and cyan inks for red and blue hues, respectively. This transition aimed to establish a more versatile color gamut achievable with only three primary colors. In 1949, a document in the printing industry stated: “The four-color set comprises Yellow, Red (magenta), Blue (cyan), Black”. This practice of labeling magenta, yellow, and cyan as red, yellow, and blue persisted until 1961. As the hues evolved, the printing industry maintained the use of the traditional terms red, yellow, and blue. Consequently, pinpointing the exact date of origin for CMYK, in which cyan serves as a primary color, proves challenging.

In August 1991, the HP Deskwriter 500C became the first Deskwriter to offer color printing as an option. It used interchangeable black and color (cyan, magenta, and yellow) inkjet print cartridges. With the inclusion of cyan ink in printers, the term "cyan" has become widely recognized in both home and office settings. According to TUP/Technology User Profile 2020, approximately 70% of online American adults regularly use a home printer.

Etymology and terminology
Its name is derived from the Ancient Greek word kyanos (κύανος), meaning "dark blue enamel, Lapis lazuli". It was formerly known as "cyan blue" or cyan-blue, and its first recorded use as a color name in English was in 1879. Further origins of the color name can be traced back to a dye produced from the cornflower (Centaurea cyanus).

In most languages, 'cyan' is not a basic color term and it phenomenologically appears as a greenish vibrant hue of blue to most English speakers. Other English terms for this "borderline" hue region include blue green, aqua, turquoise, teal, and grue.

Web colors cyan and aqua
The web color cyan shown at right is a secondary color in the RGB color model, which uses combinations of red, green and blue light to create all the colors on computer and television displays. In X11 colors, this color is called both cyan and aqua. In the HTML color list, this same color is called aqua.

The web colors are more vivid than the cyan used in the CMYK color system, and the web colors cannot be accurately reproduced on a printed page. To reproduce the web color cyan in inks, it is necessary to add some white ink to the printer's cyan below, so when it is reproduced in printing, it is not a primary subtractive color. It is called aqua (a name in use since 1598) because it is a color commonly associated with water, such as the appearance of the water at a tropical beach.

Process cyan
Cyan is also one of the common inks used in four-color printing, along with magenta, yellow, and black; this set of colors is referred to as CMYK. In printing, the cyan ink is sometimes known as printer's cyan, process cyan, or process blue.

While both the additive secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink is typically more saturated than the RGB secondary cyan, depending on what RGB color space and ink are considered. That is, process cyan is usually outside the RGB gamut, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color that is pure cyan ink. This is because real-world subtractive (unlike additive) color mixing does not consistently produce the same result when mixing apparently identical colors, since the specific frequencies filtered out to produce that color affect how it interacts with other colors. Phthalocyanine blue is one such commonly used pigment. A typical formulation of process cyan is shown in the color box on the right.

Color of water

 * Pure water is nearly colorless. However, it does absorb slightly more red light than blue, giving significant volumes of water a bluish tint; increased scattering of blue light due to fine particles in the water shifts the blue color toward green, for a typically cyan net color.

Cyan and cyanide

 * Cyanide derives its name from Prussian blue, a blue pigment containing the cyanide ion.

Bacteria

 * Cyanobacteria (sometimes called blue-green algae) are an important link in the food chain.

Astronomy

 * The planet Uranus is colored cyan because of the abundance of methane in its atmosphere. Methane absorbs red light and reflects the blue-green light which allows observers to see it as cyan.

Energy

 * Natural gas (methane), used by many for home cooking on gas stoves, has a cyan colored flame when burned with a mixture of air.

Photography and film

 * Cyanotype, or blueprint, a monochrome photographic printing process that predates the use of the word cyan as a color, yields a deep cyan-blue colored print based on the Prussian blue pigment.
 * Cinecolor, a bi-pack color process, the photographer would load a standard camera with two films, one orthochromatic, dyed red, and a panchromatic strip behind it. Color light would expose the cyan record on the ortho stock, which also acted as a filter, exposing only red light to the panchromatic film stock.

Medicine

 * Cyanosis is an abnormal blueness of the skin, usually a sign of poor oxygen intake; patients are typically described as being "cyanotic".
 * Cyanopsia is a color vision defect where vision is tinted blue. This can be a drug-induced side effect or experienced after cataract removal.

title: Cyan


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Talk:Cultural movement

Untitled

 * See also periodization.
 * Consider moving or copying the style lists into respective genres, once the genre pages exist.
 * Article's generalizations seem to be compatible with high school world history texts.
 * Renaissance shouldn't be called the "golden age of theater and architecture".
 * It is "tricky" to pick date ranges for the various "renaissances" in different areas. — Preceding unsigned comment added by BryceHarrington (talk • contribs) 20:01, 18 August 2001 (UTC)

I assume something should be said on Cultural movement about the Enlightenment. However, I personally have no idea what. :-)

Any takers? (27 September 2001) — Preceding unsigned comment added by 157.178.1.xxx (talk) 19:38, 27 September 2001 (UTC)

Actually, I think the most "tricky" part about this article is that there is very little info offered about cultural movements in non-Western cultures? Granted, I'm no expert on the subject (and will reluctantly admit to having not adequately studied in this area of sociology/anthropology) but I feel pretty certain similar movements of cultural change could be ID'd in other areas of the world at other time periods. The spread of Buddhism throughout India & SE Asia perhaps? The cultural effects of industrialization in Japan (or would that qualify as cultural imperialism?). Or how about the addition of horses to the lifestyles & societies of the indigenous peoples of the American Great Plains? (21 Ocotober 2001) — Preceding unsigned comment added by Latexture (talk • contribs) 15:05, 21 October 2001 (UTC)

From the article:

 * Incidentalism Commensing 1995 and ongoing Idiosyntactix incident. Zen-like theorectical and practical applications of the unpreconceived. Incidentalism holds all art as both original and derivative. Artifact (or commodity) is the result of artistic practice. Art objects may be owned; however, all intellectual property is fraud.

So, you're saying that "Incidentalism" is a major cultural movement, comparable with the others listed here, rather than a small group of web pranksters? Please justify this with evidence from independent sources. — Preceding unsigned comment added by 213.253.39.225 (talk) 20:05, 20 December 2002 (UTC)

Proposal: remove Neen
I can't find any evidence that Neen is indeed a de-facto art movement. It appears to be a small group of artists who are willing to put their names behind the idea of one man -- Miltos Manetas. Judging by the amount of web content refering to Neen, since it's inception in 2000 the movement has not make a wide impact. Claims that this is the first time a movement have addressed the computer medium are exegerated (IMO). The concept is now well-covered by the Neen page (I re-wrote it recently). I suggest either removing Neen from this page entirely or, if there are objections to that, converting it to a one line link. --Oliver Crow 20:09, 15 Jan 2004 (UTC)

Links !!!!
Does anyone think it is a good idea to add commercial links on this site? i don`t like it, because mostly everything is shaped by culture so what link is right?

New concept: create a Self-declared art movement page. --Oliver Crow 20:32, 15 Jan 2004 (UTC)

Merge
This should be merged with Social movement, I think. --Piotr Konieczny aka Prokonsul Piotrus Talk 18:41, 21 July 2005 (UTC)
 * After half a year to think on this :p I'd rather move this article to cultural change. Comments?--Piotr Konieczny aka Prokonsul Piotrus Talk 04:05, 23 January 2006 (UTC)

They are all distinct subjects and should have their own articles.--Sum (talk) 10:52, 21 May 2010 (UTC)

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title: Talk:Cultural movement


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Conventional insulin therapy

Conventional insulin therapy is a therapeutic regimen for treatment of diabetes mellitus which contrasts with the newer intensive insulin therapy.

This older method (prior to the development home blood glucose monitoring) is still in use in a proportion of cases.

Characteristics
Conventional insulin therapy is characterized by:
 * Insulin injections of a mixture of regular (or rapid) and intermediate acting insulin are performed two times a day, or to improve overnight glucose, mixed in the morning to cover breakfast and lunch, but with regular (or rapid) acting insulin alone for dinner and intermediate acting insulin at bedtime (instead of being mixed in at dinner).
 * Meals are scheduled to match the anticipated peaks in the insulin profiles.
 * The target range for blood glucose levels is higher than is desired in the intensive regimen.
 * Frequent measurements of blood glucose levels were not used.

Effects
The down side of this method is that it is difficult to achieve as good results of glycemic control as with intensive insulin therapy. The advantage is that, for diabetics with a regular lifestyle, the regime is less intrusive than the intensive therapy.

title: Conventional insulin therapy


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Talk:Chemical element

Semi-protected edit request on 16 September 2023
Could someone please remove some of the templates added in this diff, which seem to be questionably relevant to the article. Specifically please could the Abiogenesis timeline be removed, as this article has little to do with the origin of life, Could the Industries be removed because I don't see how any of the links in it are relevant, and could the Diatomic elements template be removed because it duplicates the contents of the article and I don't see why sorting out diatomic elements is relevant here. Thank you. 192.76.8.91 (talk) 12:25, 16 September 2023 (UTC)

 * as the editor who added these templates, any thoughts? Bestagon ⬡ 03:02, 20 September 2023 (UTC)
 * ✅ * Pppery * it has begun... 22:02, 7 October 2023 (UTC)

Semi-protected edit request on 12 December 2023
This sentence is confusing since it implies that atoms can have more than one atomic number. FROM: This is in contrast to chemical compounds and mixtures, which contain atoms with more than one atomic number.

TO: Ben said.This is in contrast to chemical compounds and mixtures, which contain more than one type of atom with different atomic numbers. CrazyCat138 (talk) 02:41, 12 December 2023 (UTC)
 * ✅ – I've changed it to ... atoms with different atomic numbers because "more than one type" appears redundant to "different atomic numbers" in the proposed replacement. Tollens (talk) 04:28, 12 December 2023 (UTC)

Semi-protected edit request on 7 February 2024
Change By 1914, eighty-seven elements were known, all naturally occurring .(See Timeline of chemical element discoveries) The remaining naturally occurring elements were discovered or isolated in subsequent decades, and various additional elements have also been produced synthetically, with much of that work pioneered by Glenn T. Seaborg. to By 1914, eighty-seven elements were known, all naturally occurring. (See Timeline of chemical element discoveries). The remaining naturally occurring elements were discovered or isolated in subsequent decades, and various additional elements have also been produced synthetically, with much of that work pioneered by Glenn T. Seaborg. or By 1914, eighty-seven elements were known, all naturally occurring (see Timeline of chemical element discoveries). The remaining naturally occurring elements were discovered or isolated in subsequent decades, and various additional elements have also been produced synthetically, with much of that work pioneered by Glenn T. Seaborg. Jiminy Cricket the Third (talk) 23:17, 7 February 2024 (UTC)
 * ✅ VQuakr (talk) 23:29, 7 February 2024 (UTC)

Isotopes
Isotopes are mentioned in multiple sections but there is nothing about them in the lead. I think that should be rectified. Praemonitus (talk) 05:10, 3 March 2024 (UTC)

Boyle section rewrite
Rewrite needed of the Boyle section; it's like 75% blockquotes. Quotes should be limited in their usage, as discussed at MOS:QUOTATIONS. VQuakr (talk) 18:44, 13 March 2024 (UTC)

title: Talk:Chemical element


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Cream

Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process is accelerated by using centrifuges called "separators". In many countries, it is sold in several grades depending on the total butterfat content. It can be dried to a powder for shipment to distant markets, and contains high levels of saturated fat.

Cream skimmed from milk may be called "sweet cream" to distinguish it from cream skimmed from whey, a by-product of cheese-making. Whey cream has a lower fat content and tastes more salty, tangy, and "cheesy". In many countries partially fermented cream is also sold: sour cream, crème fraîche, and so on. Both forms have many culinary uses in both sweet and savoury dishes.

Cream produced by cattle (particularly Jersey cattle) grazing on natural pasture often contains some carotenoid pigments derived from the plants they eat; traces of these intensely colored pigments give milk a slightly yellow tone, hence the name of the yellowish-white color: cream. Carotenoids are also the origin of butter's yellow color. Cream from goat's milk, water buffalo milk, or from cows fed indoors on grain or grain-based pellets, is white.

Cuisine
Cream is used as an ingredient in many foods, including ice cream, many sauces, soups, stews, puddings, and some custard bases, and is also used for cakes. Whipped cream is served as a topping on ice cream sundaes, milkshakes, lassi, eggnog, sweet pies, strawberries, blueberries, or peaches. Cream is also used in Indian curries such as masala dishes.

Cream (usually light/single cream or half and half) may be added to coffee.

Both single and double cream (see Types for definitions) can be used in cooking. Double cream or full-fat crème fraîche is often used when the cream is added to a hot sauce, to prevent it separating or "splitting". Double cream can be thinned with milk to make an approximation of single cream.

The French word crème denotes not only dairy cream but also other thick liquids such as sweet and savory custards, which are normally made with milk, not cream.

Types

Different grades of cream are distinguished by their fat content, whether they have been heat-treated, whipped, and so on. In many jurisdictions, there are regulations for each type.

Australia and New Zealand
The Australia New Zealand Food Standards Code – Standard 2.5.2 – Defines cream as a milk product comparatively rich in fat, in the form of an emulsion of fat-in-skim milk, which can be obtained by separation from milk. Cream sold without further specification must contain no less than 350 g/kg (35%) milk fat.

Manufacturers labels may distinguish between different fat contents, a general guideline is as follows:

Canada
Canadian cream definitions are similar to those used in the United States, except for "light cream", which is very low-fat cream, usually with 5 or 6 percent butterfat. Specific product characteristics are generally uniform throughout Canada, but names vary by both geographic and linguistic area and by manufacturer: "coffee cream" may be 10 or 18 percent cream and "half-and-half" (crème légère) may be 3, 5, 6 or 10 percent, all depending on location and brand.

Regulations allow cream to contain acidity regulators and stabilizers. For whipping cream, allowed additives include skim milk powder (≤ 0.25%), glucose solids (≤ 0.1%), calcium sulphate (≤ 0.005%), and xanthan gum (≤ 0.02%). The content of milk fat in canned cream must be displayed as a percentage followed by "milk fat", "B.F", or "M.F".

France
In France, the use of the term "cream" for food products is defined by the decree 80-313 of April 23, 1980. It specifies the minimum rate of milk fat (12%) as well as the rules for pasteurisation or UHT sterilisation. The mention "crème fraîche" (fresh cream) can only be used for pasteurised creams conditioned on production site within 24h after pasteurisation. Even if food additives complying with French and European laws are allowed, usually, none will be found in plain "crèmes" and "crèmes fraîches" apart from lactic ferments (some low cost creams (or close to creams) can contain thickening agents, but rarely). Fat content is commonly shown as "XX% M.G." ("matière grasse").

Russia
Russia, as well as other EAC countries, legally separates cream into two classes: normal (10–34% butterfat) and heavy (35–58%), but the industry has pretty much standardized around the following types:

Sweden
In Sweden, cream is usually sold as:
 * Matlagningsgrädde ("cooking cream"), 10–15%
 * Kaffegrädde ("Coffee cream"), 10–12%, earlier mostly 12%
 * Vispgrädde (whipping cream), 36–40%, the 36% variant often has additives.

Mellangrädde (27%) is, nowadays, a less common variant. Gräddfil (usually 12%) and Creme Fraiche (usually around 35%) are two common sour cream products.

Switzerland
In Switzerland, the types of cream are legally defined as follows:

Sour cream and crème fraîche (German: Sauerrahm, Crème fraîche; French: crème acidulée, crème fraîche; Italian: panna acidula, crème fraîche) are defined as cream soured by bacterial cultures.

Thick cream (German: verdickter Rahm; French: crème épaissie; Italian: panna addensata) is defined as cream thickened using thickening agents.

United Kingdom
In the United Kingdom, these types of cream are produced. Fat content must meet the Food Labelling Regulations 1996.

United States
In the United States, cream is usually sold as:

Not all grades are defined by all jurisdictions, and the exact fat content ranges vary. The above figures, except for "manufacturer's cream", are based on the Code of Federal Regulations, Title 21, Part 131.

Processing and additives
Cream may have thickening agents and stabilizers added. Thickeners include sodium alginate, carrageenan, gelatine, sodium bicarbonate, tetrasodium pyrophosphate, and alginic acid.

Other processing may be carried out. For example, cream has a tendency to produce oily globules (called "feathering") when added to coffee. The stability of the cream may be increased by increasing the non-fat solids content, which can be done by partial demineralisation and addition of sodium caseinate, although this is expensive.

Other cream products

Butter is made by churning cream to separate the butterfat and buttermilk. This can be done by hand or by machine.

Whipped cream is made by whisking or mixing air into cream with more than 30% fat, to turn the liquid cream into a soft solid. Nitrous oxide, from whipped-cream chargers may also be used to make whipped cream.

Sour cream, produced in many countries, is cream (12 to 16% or more milk fat) that has been subjected to a bacterial culture that produces lactic acid (0.5%+), which sours and thickens it.

Crème fraîche (28% milk fat) is slightly soured with bacterial culture, but not as sour or as thick as sour cream. Mexican crema (or cream espesa) is similar to crème fraîche.

Smetana is a heavy cream-derived (15–40% milk fat) Central and Eastern European sweet or sour cream.

Rjome or rømme is Norwegian sour cream containing 35% milk fat, similar to Icelandic sýrður rjómi.

Clotted cream in the United Kingdom is made through a process that starts by slowly heating whole milk to produce a very high-fat (55%) product, similar to Indian malai.

Reduced cream is a cream product in New Zealand, often used to make Kiwi dip.

Other items called "cream"
Some non-edible substances are called creams due to their consistency: shoe cream is runny, unlike regular waxy shoe polish; hand/body "creme" or "skin cream" is meant for moisturizing the skin.

Regulations in many jurisdictions restrict the use of the word cream for foods. Words such as creme, kreme, creame, or whipped topping (e.g., Cool Whip) are often used for products which cannot legally be called cream, though in some jurisdictions even these spellings may be disallowed, for example under the doctrine of idem sonans. Oreo and Hydrox cookies are a type of sandwich cookie in which two biscuits have a soft, sweet filling between them that is called "crème filling." In some cases, foods can be described as cream although they do not contain predominantly milk fats; for example, in Britain, "ice cream" can contain non-milk fat (declared on the label) in addition to or instead of cream, and salad cream is the customary name for a non-dairy condiment that has been produced since the 1920s.

In other languages, cognates of "cream" are also sometimes used for non-food products, such as fogkrém (Hungarian for toothpaste), or Sonnencreme (German for sunscreen).

Some products are described as "cream alternatives". For example, Elmlea Double, etc. are blends of buttermilk or lentils and vegetable oil with other additives sold by Upfield in the United Kingdom packaged and shelved in the same way as cream, labelled as having "a creamy taste".

title: Cream


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Chemical vapor deposition

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.

In typical CVD, the wafer (substrate) is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.

Microfabrication processes widely use CVD to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon (dioxide, carbide, nitride, oxynitride), carbon (fiber, nanofibers, nanotubes, diamond and graphene), fluorocarbons, filaments, tungsten, titanium nitride and various high-κ dielectrics.

The term chemical vapour deposition was coined in 1960 by John M. Blocher, Jr. who intended to differentiate chemical from physical vapour deposition (PVD).

Types

CVD is practiced in a variety of formats. These processes generally differ in the means by which chemical reactions are initiated.
 * Classified by operating conditions:
 * Atmospheric pressure CVD (APCVD) – CVD at atmospheric pressure.
 * Low-pressure CVD (LPCVD) – CVD at sub-atmospheric pressures. Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer.
 * Ultrahigh vacuum CVD (UHVCVD) – CVD at very low pressure, typically below 10−6 Pa (≈ 10−8 torr). Note that in other fields, a lower division between high and ultra-high vacuum is common, often 10−7 Pa.
 * Sub-atmospheric CVD (SACVD) – CVD at sub-atmospheric pressures. Uses tetraethyl orthosilicate (TEOS) and ozone to fill high aspect ratio Si structures with silicon dioxide (SiO2).

Most modern CVD is either LPCVD or UHVCVD.
 * Classified by physical characteristics of vapor:
 * Aerosol assisted CVD (AACVD) – CVD in which the precursors are transported to the substrate by means of a liquid/gas aerosol, which can be generated ultrasonically. This technique is suitable for use with non-volatile precursors.
 * Direct liquid injection CVD (DLICVD) – CVD in which the precursors are in liquid form (liquid or solid dissolved in a convenient solvent). Liquid solutions are injected in a vaporization chamber towards injectors (typically car injectors). The precursor vapors are then transported to the substrate as in classical CVD. This technique is suitable for use on liquid or solid precursors. High growth rates can be reached using this technique.
 * Classified by type of substrate heating:
 * Hot wall CVD – CVD in which the chamber is heated by an external power source and the substrate is heated by radiation from the heated chamber walls.
 * Cold wall CVD – CVD in which only the substrate is directly heated either by induction or by passing current through the substrate itself or a heater in contact with the substrate. The chamber walls are at room temperature.
 * Plasma methods (see also Plasma processing):
 * Microwave plasma-assisted CVD (MPCVD)
 * Plasma-enhanced CVD (PECVD) – CVD that utilizes plasma to enhance chemical reaction rates of the precursors. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The lower temperatures also allow for the deposition of organic coatings, such as plasma polymers, that have been used for nanoparticle surface functionalization.
 * Remote plasma-enhanced CVD (RPECVD) – Similar to PECVD except that the wafer substrate is not directly in the plasma discharge region. Removing the wafer from the plasma region allows processing temperatures down to room temperature.
 * Low-energy plasma-enhanced chemical vapor deposition (LEPECVD) - CVD employing a high density, low energy plasma to obtain epitaxial deposition of semiconductor materials at high rates and low temperatures.
 * Atomic-layer CVD (ALCVD) – Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.
 * Combustion chemical vapor deposition (CCVD) – Combustion Chemical Vapor Deposition or flame pyrolysis is an open-atmosphere, flame-based technique for depositing high-quality thin films and nanomaterials.
 * Hot filament CVD (HFCVD) – also known as catalytic CVD (Cat-CVD) or more commonly, initiated CVD, this process uses a hot filament to chemically decompose the source gases. The filament temperature and substrate temperature thus are independently controlled, allowing colder temperatures for better absorption rates at the substrate and higher temperatures necessary for decomposition of precursors to free radicals at the filament.
 * Hybrid physical-chemical vapor deposition (HPCVD) – This process involves both chemical decomposition of precursor gas and vaporization of a solid source.
 * Metalorganic chemical vapor deposition (MOCVD) – This CVD process is based on metalorganic precursors.
 * Rapid thermal CVD (RTCVD) – This CVD process uses heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas-phase reactions that can lead to particle formation.
 * Vapor-phase epitaxy (VPE)
 * Photo-initiated CVD (PICVD) – This process uses UV light to stimulate chemical reactions. It is similar to plasma processing, given that plasmas are strong emitters of UV radiation. Under certain conditions, PICVD can be operated at or near atmospheric pressure.
 * Laser chemical vapor deposition (LCVD) - This CVD process uses lasers to heat spots or lines on a substrate in semiconductor applications. In MEMS and in fiber production the lasers are used rapidly to break down the precursor gas—process temperature can exceed 2000 °C—to build up a solid structure in much the same way as laser sintering based 3-D printers build up solids from powders.

Uses
CVD is commonly used to deposit conformal films and augment substrate surfaces in ways that more traditional surface modification techniques are not capable of. CVD is extremely useful in the process of atomic layer deposition at depositing extremely thin layers of material. A variety of applications for such films exist. Gallium arsenide is used in some integrated circuits (ICs) and photovoltaic devices. Amorphous polysilicon is used in photovoltaic devices. Certain carbides and nitrides confer wear-resistance. Polymerization by CVD, perhaps the most versatile of all applications, allows for super-thin coatings which possess some very desirable qualities, such as lubricity, hydrophobicity and weather-resistance to name a few. The CVD of metal-organic frameworks, a class of crystalline nanoporous materials, has recently been demonstrated. Recently scaled up as an integrated cleanroom process depositing large-area substrates, the applications for these films are anticipated in gas sensing and low-κ dielectrics. CVD techniques are advantageous for membrane coatings as well, such as those in desalination or water treatment, as these coatings can be sufficiently uniform (conformal) and thin that they do not clog membrane pores.

Polysilicon
Polycrystalline silicon is deposited from trichlorosilane (SiHCl3) or silane (SiH4), using the following reactions:
 * SiHCl3 → Si + Cl2 +  HCl
 * SiH4 → Si + 2 H2

This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70–80% nitrogen. Temperatures between 600 and 650 °C and pressures between 25 and 150 Pa yield a growth rate between 10 and 20 nm per minute. An alternative process uses a hydrogen-based solution. The hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate. Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine decrease it.

Silicon dioxide
Silicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common source gases include silane and oxygen, dichlorosilane (SiCl2H2) and nitrous oxide (N2O), or tetraethylorthosilicate (TEOS; Si(OC2H5)4). The reactions are as follows:

 * SiH4 + O2 → SiO2 + 2 H2

 * SiCl2H2 + 2 N2O → SiO2 + 2 N2 + 2 HCl

 * Si(OC2H5)4 → SiO2 + byproducts

The choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C, resulting in a layer of low- temperature oxide (LTO). However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits nonconformally. Any of these reactions may be used in LPCVD, but the silane reaction is also done in APCVD. CVD oxide invariably has lower quality than thermal oxide, but thermal oxidation can only be used in the earliest stages of IC manufacturing.

Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5–15% impurities by mass are often used for this purpose. In addition, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth out uneven surfaces. P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen:

 * 4 PH3 + 5 O2 → 2 P2O5 + 6 H2

Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; around 850 °C is achievable with glasses containing around 5 weight % of both constituents, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient moisture to produce phosphoric acid. Crystals of BPO4 can also precipitate from the flowing glass on cooling; these crystals are not readily etched in the standard reactive plasmas used to pattern oxides, and will result in circuit defects in integrated circuit manufacturing.

Besides these intentional impurities, CVD oxide may contain byproducts of the deposition. TEOS produces a relatively pure oxide, whereas silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.

Lower temperature deposition of silicon dioxide and doped glasses from TEOS using ozone rather than oxygen has also been explored (350 to 500 °C). Ozone glasses have excellent conformality but tend to be hygroscopic – that is, they absorb water from the air due to the incorporation of silanol (Si-OH) in the glass. Infrared spectroscopy and mechanical strain as a function of temperature are valuable diagnostic tools for diagnosing such problems.

Silicon nitride
Silicon nitride is often used as an insulator and chemical barrier in manufacturing ICs. The following two reactions deposit silicon nitride from the gas phase:

 * 3 SiH4 + 4 NH3 → Si3N4 + 12 H2

 * 3 SiCl2H2 + 4 NH3 → Si3N4 + 6 HCl + 6 H2

Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which may crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (1016 Ω·cm and 10 MV/cm, respectively).

Another two reactions may be used in plasma to deposit SiNH:

 * 2 SiH4 + N2 → 2 SiNH + 3 H2

 * SiH4 + NH3 → SiNH + 3 H2

These films have much less tensile stress, but worse electrical properties (resistivity 106 to 1015 Ω·cm, and dielectric strength 1 to 5 MV/cm).

Metals
Tungsten CVD, used for forming conductive contacts, vias, and plugs on a semiconductor device, is achieved from tungsten hexafluoride (WF6), which may be deposited in two ways:

 * WF6 → W + 3 F2
 * WF6 + 3 H2 → W + 6 HF

Other metals, notably aluminium and copper, can be deposited by CVD. , commercially cost-effective CVD for copper did not exist, although volatile sources exist, such as Cu(hfac)2. Copper is typically deposited by electroplating. Aluminium can be deposited from triisobutylaluminium (TIBAL) and related organoaluminium compounds.

CVD for molybdenum, tantalum, titanium, nickel is widely used. These metals can form useful silicides when deposited onto silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorides. Nickel, molybdenum, and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the chloride deposition reaction is as follows:

 * 2 MCl5 + 5 H2 → 2 M + 10 HCl

whereas the carbonyl decomposition reaction can happen spontaneously under thermal treatment or acoustic cavitation and is as follows:

 * M(CO)n → M + n CO

the decomposition of metal carbonyls is often violently precipitated by moisture or air, where oxygen reacts with the metal precursor to form metal or metal oxide along with carbon dioxide.

Niobium(V) oxide layers can be produced by the thermal decomposition of niobium(V) ethoxide with the loss of diethyl ether according to the equation:

 * 2 Nb(OC2H5)5 → Nb2O5 + 5 C2H5OC2H5

Graphene
Many variations of CVD can be utilized to synthesize graphene. Although many advancements have been made, the processes listed below are not commercially viable yet.
 * Carbon source

The most popular carbon source that is used to produce graphene is methane gas. One of the less popular choices is petroleum asphalt, notable for being inexpensive but more difficult to work with.

Although methane is the most popular carbon source, hydrogen is required during the preparation process to promote carbon deposition on the substrate. If the flow ratio of methane and hydrogen are not appropriate, it will cause undesirable results. During the growth of graphene, the role of methane is to provide a carbon source, the role of hydrogen is to provide H atoms to corrode amorphous C, and improve the quality of graphene. But excessive H atoms can also corrode graphene. As a result, the integrity of the crystal lattice is destroyed, and the quality of graphene is deteriorated. Therefore, by optimizing the flow rate of methane and hydrogen gases in the growth process, the quality of graphene can be improved. The use of catalyst is viable in changing the physical process of graphene production. Notable examples include iron nanoparticles, nickel foam, and gallium vapor. These catalysts can either be used in situ during graphene buildup, or situated at some distance away at the deposition area. Some catalysts require another step to remove them from the sample material.
 * Use of catalyst

The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process. Physical conditions such as surrounding pressure, temperature, carrier gas, and chamber material play a big role in production of graphene.
 * Physical conditions

Most systems use LPCVD with pressures ranging from 1 to 1500 Pa. However, some still use APCVD. Low pressures are used more commonly as they help prevent unwanted reactions and produce more uniform thickness of deposition on the substrate.

On the other hand, temperatures used range from 800 to 1050 °C. High temperatures translate to an increase of the rate of reaction. Caution has to be exercised as high temperatures do pose higher danger levels in addition to greater energy costs. Hydrogen gas and inert gases such as argon are flowed into the system. These gases act as a carrier, enhancing surface reaction and improving reaction rate, thereby increasing deposition of graphene onto the substrate. Standard quartz tubing and chambers are used in CVD of graphene. Quartz is chosen because it has a very high melting point and is chemically inert. In other words, quartz does not interfere with any physical or chemical reactions regardless of the conditions. Raman spectroscopy, X-ray spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are used to examine and characterize the graphene samples.
 * Carrier gas
 * Chamber material
 * Methods of analysis of results

Raman spectroscopy is used to characterize and identify the graphene particles; X-ray spectroscopy is used to characterize chemical states; TEM is used to provide fine details regarding the internal composition of graphene; SEM is used to examine the surface and topography.

Sometimes, atomic force microscopy (AFM) is used to measure local properties such as friction and magnetism.

Cold wall CVD technique can be used to study the underlying surface science involved in graphene nucleation and growth as it allows unprecedented control of process parameters like gas flow rates, temperature and pressure as demonstrated in a recent study. The study was carried out in a home-built vertical cold wall system utilizing resistive heating by passing direct current through the substrate. It provided conclusive insight into a typical surface-mediated nucleation and growth mechanism involved in two-dimensional materials grown using catalytic CVD under conditions sought out in the semiconductor industry.

Graphene nanoribbon
In spite of graphene's exciting electronic and thermal properties, it is unsuitable as a transistor for future digital devices, due to the absence of a bandgap between the conduction and valence bands. This makes it impossible to switch between on and off states with respect to electron flow. Scaling things down, graphene nanoribbons of less than 10 nm in width do exhibit electronic bandgaps and are therefore potential candidates for digital devices. Precise control over their dimensions, and hence electronic properties, however, represents a challenging goal, and the ribbons typically possess rough edges that are detrimental to their performance.

Diamond

CVD can be used to produce a synthetic diamond by creating the circumstances necessary for carbon atoms in a gas to settle on a substrate in crystalline form. CVD of diamonds has received much attention in the materials sciences because it allows many new applications that had previously been considered too expensive. CVD diamond growth typically occurs under low pressure (1–27 kPa; 0.145–3.926 psi; 7.5–203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.

Using CVD, films of diamond can be grown over large areas of substrate with control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce a diamond, the result was typically very small free-standing diamonds of varying sizes. With CVD diamond, growth areas of greater than fifteen centimeters (six inches) in diameter have been achieved, and much larger areas are likely to be successfully coated with diamond in the future. Improving this process is key to enabling several important applications.

The growth of diamond directly on a substrate allows the addition of many of diamond's important qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, layering diamond onto high heat-producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond's hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate. Diamond's very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (polytetrafluoroethylene) and strong lipophilicity would make it a nearly ideal non-stick coating for cookware if large substrate areas could be coated economically.

CVD growth allows one to control the properties of the diamond produced. In the area of diamond growth, the word "diamond" is used as a description of any material primarily made up of sp3-bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single-crystal diamond can be made containing various dopants. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon, while others are not. These different factors affect the diamond's hardness, smoothness, conductivity, optical properties and more.

Chalcogenides
Commercially, mercury cadmium telluride is of continuing interest for detection of infrared radiation. Consisting of an alloy of CdTe and HgTe, this material can be prepared from the dimethyl derivatives of the respective elements.

title: Chemical vapor deposition


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CN Tower

The CN Tower (Tour CN) is a 553.3 m concrete communications and observation tower in Toronto, Ontario, Canada. Completed in 1976, it is located in downtown Toronto, built on the former Railway Lands. Its name "CN" referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets prior to the company's privatization in 1995, it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for the government's real estate portfolio.

The CN Tower held the record for the world's tallest free-standing structure for 32 years, from 1975 until 2007, when it was surpassed by the Burj Khalifa, and was the world's tallest tower until 2009 when it was surpassed by the Canton Tower. It is currently the tenth-tallest free-standing structure in the world and remains the tallest free-standing structure on land in the Western Hemisphere. In 1995, the CN Tower was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers.

It is a signature icon of Toronto's skyline and attracts more than two million international visitors annually. It houses several observation decks, a revolving restaurant at some 1150 ft, and an entertainment complex.

History

The original concept of the CN Tower was first conceived in 1968 when the Canadian National Railway wanted to build a large television and radio communication platform to serve the Toronto area, and to demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972.

The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant after the opening of the MacMillan Yard north of the city in 1965 (then known as Toronto Yard). Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division).

As Toronto grew rapidly during the late 1960s and early 1970s, multiple skyscrapers were constructed in the downtown core, most notably First Canadian Place, which has Bank of Montreal's head offices. The reflective nature of the new buildings reduced the quality of broadcast signals, requiring new, higher antennas that were at least 300 m tall. The radio wire is estimated to be 102 m long in 44 pieces, the heaviest of which weighs around 8 t.

At the time, most data communications took place over point-to-point microwave links, whose dish antennas covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area.

The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the SkyPod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the SkyPod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.

The idea for the main level in its current form evolved around this time, but the Space Deck (later renamed SkyPod) was not part of the plans until later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. Also around this time, it was realized that the tower could become the world's tallest free-standing structure to improve signal quality and attract tourists, and plans were changed to incorporate subtle modifications throughout the structure to this end.

Construction

The CN Tower was built by Canada Cement Company (also known as the Cement Foundation Company of Canada at the time), a subsidiary of Sweden's Skanska, a global project-development and construction group.

Construction began on February 6, 1973, with massive excavations at the tower base for the foundation. By the time the foundation was complete, 56000 t of earth and shale were removed to a depth of 15 m in the centre, and a base incorporating 7000 m3 of concrete with 450 t of rebar and 36 t of steel cable had been built to a thickness of 6.7 m. This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.

To create the main support pillar, workers constructed a hydraulically raised slipform at the base. This was a fairly unprecedented engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about 6 m per day as the concrete below set. Concrete was poured Monday to Friday (not continuously) by a small team of people until February 22, 1974, at which time it had already become the tallest structure in Canada, surpassing the recently built 381 m tall Inco Superstack in Sudbury, built using similar methods.

The tower contains 40500 m3 of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massive plumb bobs hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only 29 mm.

In August 1974, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were used to create the brackets that support the main level, as well as a base for the construction of the main level itself. The Space Deck (currently named SkyPod) was built of concrete poured into a wooden frame attached to rebar at the lower level deck, and then reinforced with a large steel compression band around the outside.

While still under construction, the CN Tower officially became the world's tallest free-standing structure on March 31, 1975.

The antenna was originally to be raised by crane as well, but, during construction, the Sikorsky S-64 Skycrane helicopter became available when the United States Army sold one to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections.

The flights of the antenna pieces were a minor tourist attraction of their own, and the schedule was printed in local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three and a half weeks instead of the planned six months. The tower was topped-off on April 2, 1975, after 26 months of construction, officially capturing the height record from Moscow's Ostankino Tower, and bringing the total mass to 118000 t.

Two years into the construction, plans for Metro Centre were scrapped, leaving the tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."

Opening
The CN Tower opened on June 26, 1976. The construction costs of approximately CA$63 million ($ in dollars) were repaid in fifteen years.

From the mid-1970s to the mid-1980s, the CN Tower was practically the only development along Front Street West; it was still possible to see Lake Ontario from the foot of the CN Tower due to the expansive parking lots and lack of development in the area at the time. As the area around the tower was developed, particularly with the completion of the Metro Toronto Convention Centre (north building) in 1984 and SkyDome in 1989 (renamed Rogers Centre in 2005), the former Railway Lands were redeveloped and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the SkyWalk in 1989, which connected the tower and SkyDome to the nearby Union Station railway and subway station, and, in turn, to the city's Path underground pedestrian system. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a boom in condominium construction in the first quarter of the 21st century, as well as the 2013 opening of the Ripley's Aquarium by the base of the tower.

Early years
When the CN Tower opened in 1976, there were three public observation points: the SkyPod (then known as the Space Deck) that stands at 447 m, the Indoor Observation Level (later named Indoor Lookout Level) at 346 m, and the Outdoor Observation Terrace (at the same level as the Glass Floor) at 342 m. One floor above the Indoor Observation Level was the Top of Toronto Restaurant, which completed a revolution once every 72 minutes.

The tower would garner worldwide media attention when stuntman Dar Robinson jumped off the CN Tower on two occasions in 1979 and 1980. The first was for a scene from the movie Highpoint, in which Robinson received CA$250,000 ($ in dollars) for the stunt. The second was for a personal documentary. The first stunt had him use a parachute which he deployed three seconds before impact with the ground, while the second one used a wire decelerator attached to his back.

On June 26, 1986, the tenth anniversary of the tower's opening, high-rise firefighting and rescue advocate Dan Goodwin, in a sponsored publicity event, used his hands and feet to climb the outside of the tower, a feat he performed twice on the same day. Following both ascents, he used multiple rappels to descend to the ground.

From 1985 to 1992, the CN Tower basement level hosted the world's first flight simulator ride, Tour of the Universe, based on the flight of a Space Shuttle. The ride was replaced in 1992 with a similar attraction entitled "Space Race." It was later dismantled and replaced by two other rides in 1998 and 1999.

The 1990s and 2000s
A glass floor at an elevation of 342 m was installed in 1994. Canadian National Railway sold the tower to Canada Lands Company prior to privatizing the company in 1995, when it divested all operations not directly related to its core freight shipping businesses. The tower's name and wordmark were adjusted to remove the CN railways logo, and the tower's official name was renamed Canada's National Tower (from Canadian National Tower), though the tower is commonly called the CN Tower.

Further changes were made from 1997 to January 2004: TrizecHahn Corporation managed the tower and instituted several expansion projects including a CA$26 million entertainment expansion, the 1997 addition of two new elevators (to a total of six) and the consequential relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb. TrizecHahn also owned the Willis Tower (Sears Tower at the time) in Chicago approximately at the same time.

In 2007, light-emitting diode (LED) lights replaced the incandescent lights that lit the CN Tower at night. This was done to take advantage of the cost savings of LED lights over incandescent lights. The colour of the LED lights can change, compared to the constant white colour of the incandescent lights. On September 12, 2007, Burj Khalifa, then under construction and known as Burj Dubai, surpassed the CN Tower as the world's tallest free-standing structure on land. In 2008, glass panels were installed in one of the CN Tower elevators, which established a world record (346 m) for highest glass floor panelled elevator in the world.

2010s: EdgeWalk

On August 1, 2011, the CN Tower opened the EdgeWalk, an amusement in which thrill-seekers can walk on and around the roof of the main pod of the tower at 356 m, which is directly above the 360 Restaurant. It is the world's highest full-circle, hands-free walk. Visitors are tethered to an overhead rail system and walk around the edge of the CN Tower's main pod above the 360 Restaurant on a 1.5 m metal floor. The attraction is closed throughout the winter and during periods of electrical storms and high winds.

One of the notable guests who visited EdgeWalk was Canadian comedian Rick Mercer, featured as the first episode of the ninth season of his CBC Television news satire show, Rick Mercer Report. There, he was accompanied by Canadian pop singer Jann Arden. The episode first aired on April 10, 2013.

Pan Am Games
The tower and surrounding areas were prominent in the 2015 Pan American Games production. In the opening ceremony, a pre-recorded segment featured track-and-field athlete Bruny Surin passing the flame to sprinter Donovan Bailey on the EdgeWalk and parachuting into Rogers Centre. A fireworks display off the tower concluded both the opening and closing ceremonies.

Canada 150
On July 1, 2017, as part of the nationwide celebrations for Canada 150, which celebrated the 150th anniversary of Canadian Confederation, fireworks were once again shot from the tower in a five-minute display coordinated with the tower lights and music broadcast on a local radio station.

Closures

 * The CN Tower was closed on September 11, 2001 following the terrorist attacks on the World Trade Center.
 * The CN Tower was closed during the G20 summit on June 26–27, 2010, for security reasons, given its proximity to the Metro Toronto Convention Centre and ongoing citywide protests and riots.
 * The CN Tower was closed from 2020 to 2021 due to COVID-19 pandemic restrictions throughout Ontario.
 * The CN Tower was closed on December 16, 2021, due to glass falling off from heavy winds.

Structure

The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing the stairwells and power and plumbing connections. The tower's six elevators are located in the three inverted angles created by the Tower's hexagonal shape (two elevators per angle). Each of the three elevator shafts is lined with glass, allowing for views of the city as the glass-windowed elevators make their way through the tower. The stairwell was originally located in one of these angles (the one facing north), but was moved into the central hollow of the tower; the tower's new fifth and sixth elevators were placed in the hexagonal angle that once contained the stairwell. On top of the main concrete portion of the tower is a 102 m tall metal broadcast antenna, carrying television and radio signals. There are three visitor areas: the Glass Floor and Outdoor Observation Terrace, which are both located at an elevation of 342 m, the Indoor Lookout Level (formerly known as "Indoor Observation Level") located at 346 m, and the higher SkyPod (formerly known as "Space Deck") at 446.5 m, just below the metal antenna. The hexagonal shape is visible between the two highest areas; however, below the main deck, three large supporting legs give the tower the appearance of a large tripod.

The main deck level has seven storeys, some of which are open to the public. Below the public areas—at 338 m—is a large white donut-shaped radome containing the structure's UHF transmitters. The glass floor and outdoor observation deck are at 342 m. The glass floor has an area of 24 m2 and can withstand a pressure of 4.1 MPa. The floor's thermal glass units are 64 mm thick, consisting of a pane of 25 mm laminated glass, 25 mm airspace and a pane of 13 mm laminated glass. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature. The Horizons Cafe and the lookout level are at 346 m. The 360 Restaurant, a revolving restaurant that completes a full rotation once every 72 minutes, is at 351 m. When the tower first opened, it also featured a disco named Sparkles (at the Indoor Observation Level), billed as the highest disco and dance floor in the world.

The SkyPod was once the highest public observation deck in the world until it was surpassed by the Shanghai World Financial Center in 2008.

A metal staircase reaches the main deck level after 1,776 steps, and the SkyPod 100 m above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only except for charity stair-climb events two times during the year. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an Ontario Provincial Police officer. In 2002, Canadian Olympian and Paralympic champion Jeff Adams climbed the stairs of the tower in a specially designed wheelchair. The stairs were originally on one of the three sides of the tower (facing north), with a glass view, but these were later replaced with the third elevator pair and the stairs were moved to the inside of the core. Top climbs on the new, windowless stairwell used since around 2003 have generally been over ten minutes.

Architects

 * WZMH Architects
 * John Hamilton Andrews
 * Webb Zerafa
 * Menkes Housden with the help of Edward R. Baldwin

Falling ice danger

A freezing rain storm on March 2, 2007, resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, then winds of up to 90 km/h blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5 of the same year, police expanded the area of closed streets to include the Gardiner Expressway 310 m away from the tower as increased winds blew the ice farther, as far north as King Street West, 490 m away, where a taxicab window was shattered. Subsequently, on March 6, 2007, the Gardiner Expressway reopened after winds abated.

On April 16, 2018, falling ice from the CN Tower punctured the roof of the nearby Rogers Centre stadium, causing the Toronto Blue Jays to postpone the game that day to the following day as a doubleheader; this was the third doubleheader held at the Rogers Centre. On April 20 of the same year, the CN Tower reopened.

Safety features
In August 2000, a fire broke out at the Ostankino Tower in Moscow, killing three people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and sparked fears the tower might even collapse.

The Ostankino Tower was completed nine years before the CN Tower and is only 13 m shorter. The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower, as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited:

 * the fireproof building materials used in the tower's construction,
 * frequent and stringent safety inspections,
 * an extensive sprinkler system,
 * a 24-hour emergency monitoring operation,
 * two 68,160-litre (15,000-imperial gallon; 18,006-US gallon) water reservoirs at the top, which are automatically replenished,
 * a fire hose at the base of the structure capable of sending 2725 litres/min to any location in the tower,
 * a ban on natural gas appliances anywhere in the tower (including the restaurant in the main pod),
 * an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino Tower, which malfunctioned).

Officials also noted that the CN Tower has an excellent safety record, although there was an electrical fire in the antennas on August 16, 2017 — the tower's first fire. Moreover, other supertall structures built between 1967 and 1976 — such as the Willis Tower (formerly the Sears Tower), the World Trade Center (until its destruction on September 11, 2001), the Fernsehturm Berlin, the Aon Center, 875 North Michigan Avenue (formerly the John Hancock Center), and First Canadian Place — also have excellent safety records, which suggests that the Ostankino Tower accident was a rare safety failure, and that the likelihood of similar events occurring at other supertall structures is extremely low.

Lighting
The CN Tower was originally lit at night with incandescent lights, which were removed in 1997 because they were inefficient and expensive to repair. In June 2007, the tower was outfitted with 1,330 super-bright LED lights inside the elevator shafts, shooting over the main pod and upward to the top of the tower's mast to light the tower from dusk until 2 a.m. The official opening ceremony took place on June 28, 2007, before the Canada Day holiday weekend.

The tower changes its lighting scheme on holidays and to commemorate major events. After the 95th Grey Cup in Toronto, the tower was lit in green and white to represent the colours of the Grey Cup champion Saskatchewan Roughriders. From sundown on August 27, 2011, to sunrise the following day, the tower was lit in orange, the official colour of the New Democratic Party (NDP), to commemorate the death of federal NDP leader and leader of the official opposition Jack Layton. When former South African president Nelson Mandela died, the tower was lit in the colours of the South African flag. When former federal finance minister under Stephen Harper's Conservatives Jim Flaherty died, the tower was lit in green to reflect his Irish Canadian heritage. On the night of the attacks on Paris on November 13, 2015, the tower displayed the colours of the French flag. On June 8, 2021, the tower displayed the colours of the Toronto Maple Leafs' archrivals Montreal Canadiens after they advanced to the semifinals of 2021 Stanley Cup playoffs. The CN Tower was lit in the colours of the Ukrainian flag during the beginning of the Russian invasion of Ukraine in late February 2022.

Programmed remotely from a desktop computer with a wireless network interface controller in Burlington, Ontario, the LEDs use less energy to light than the previous incandescent lights (10% less energy than the dimly lit version and 60% less than the brightly lit version). The estimated cost to use the LEDs is $1,000 per month.

During the spring and autumn bird migration seasons, the lights are turned off to comply with the voluntary Fatal Light Awareness Program, which "encourages buildings to dim unnecessary exterior lighting to mitigate bird mortality during spring and summer migration."

Height comparisons

The CN Tower is the tallest freestanding structure in the Western Hemisphere. As of 2013, there were two other freestanding structures in the Western Hemisphere exceeding 500 m in height: the Willis Tower in Chicago, which stands at 527 m when measured to its pinnacle, and One World Trade Center in New York City, which has a pinnacle height of 541.33 m, or approximately 12 m shorter than the CN Tower. Due to the symbolism of the number 1776 (the year of the signing of the United States Declaration of Independence), the height of One World Trade Center is unlikely to be increased. The proposed Chicago Spire was expected to exceed the height of the CN Tower, but its construction was halted early due to financial difficulties amid the Great Recession, and was eventually cancelled in 2010.

"World's Tallest Tower" title
Guinness World Records has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings." In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure". Emporis and the Council on Tall Buildings and Urban Habitat both listed the CN Tower as the world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of world's tallest building to Taipei 101, which is 44 m shorter than the CN Tower. The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).

Although the CN Tower contains a restaurant, a gift shop and multiple observation levels, it does not have floors continuously from the ground, and therefore it is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH) or Emporis. CTBUH defines a building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors." The CN Tower and other similar structures—such as the Ostankino Tower in Moscow, Russia; the Oriental Pearl Tower in Shanghai, China; The Strat in Las Vegas, Nevada, United States; and the Eiffel Tower in Paris, France—are categorized as "towers", which are free-standing structures that may have observation decks and a few other habitable levels, but do not have floors from the ground up. The CN Tower was the tallest tower by this definition until 2010 (see below).

Taller than the CN Tower are numerous radio masts and towers, which are held in place by guy-wires, the tallest being the KVLY-TV mast in Blanchard, North Dakota, in the United States at 628 m tall, leading to a distinction between these and "free-standing" structures. Additionally, the Petronius Platform stands 610 m above its base on the bottom of the Gulf of Mexico near the Mississippi River Delta, but only the top 75 m of this oil and natural gas platform are above water, and the structure is thus partially supported by its buoyancy. Like the CN Tower, none of these taller structures are commonly considered buildings.

On September 12, 2007, Burj Khalifa, which is a hotel, residential and commercial building in Dubai, United Arab Emirates (formerly known as Burj Dubai before opening), passed the CN Tower's 553.33-m height. The CN Tower held the record of the tallest freestanding structure on land for over 30 years.

After Burj Khalifa had been formally recognized by the Guinness World Records as the world's tallest freestanding structure, Guinness re-certified CN Tower as the world's tallest freestanding tower. The tower definition used by Guinness was defined by the Council on Tall Buildings and Urban Habitat as 'a building in which less than 50% of the construction is usable floor space'. Guinness World Records editor-in-chief Craig Glenday announced that Burj Khalifa was not classified as a tower because it has too much usable floor space to be considered to be a tower. CN Tower still held world records for highest above ground wine cellar (in 360 Restaurant) at 351 m, highest above ground restaurant at 346 m (Horizons Restaurant), and tallest free-standing concrete tower during Guinness's recertification. The CN Tower was surpassed in 2009 by the Canton Tower in Guangzhou, China, which stands at 604 m tall, as the world's tallest tower; which in turn was surpassed by the Tokyo Skytree in 2011, which currently is the tallest tower at 634.0 m in height. The CN Tower, as of 2022, stands as the tenth-tallest free-standing structure on land, remains the tallest free-standing structure in the Western Hemisphere, and is the third-tallest tower.

Height records

Since its construction, the tower has gained the following world height records:

Use
The CN Tower has been and continues to be used as a communications tower for a number of different media and by numerous companies.

Television broadcasters
Source: Vividcomm

Radio
There is no AM broadcasting from the CN Tower. The FM transmitters are situated in a 102 m metal broadcast antenna, on top of the main concrete portion of the tower at an elevation above 446.5 m from the ground.

Source: Vividcomm

Communications

 * Bell Canada
 * Toronto Transit Commission
 * Amateur radio repeaters "2-Tango" (VHF) and "4-Tango" (440/70 cm UHF)—owned and operated by the Toronto FM Communications Society, under callsign VE3TWR

In popular culture
The CN Tower has been featured in numerous films, television shows, music recording covers, and video games. The tower also has its own official mascot, which resembles the tower itself.

 * Highpoint is a Canadian 1982 action film starring Richard Harris, Christopher Plummer and Beverly D'Angelo. It features a shot of stuntman Dar Robinson jumping off of the CN Tower in 1979.
 * Views is a 2016 studio album released on April 29, 2016 by Canadian rapper Drake. The cover artwork features Drake sitting atop the CN Tower in Toronto. Drake appeared significantly larger than life-size on the cover, and the CN Tower's Twitter account later confirmed it to be photo edited.

title: CN Tower