Last updated on 21 August 2017

Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a blue-gray metallic luster, it is a tetravalent metalloid. It is a member of group 14 in the periodic table, along with carbon above it and germanium, tin, lead, and flerovium below. It is not very reactive, although more reactive than carbon, and has great chemical affinity for oxygen; it was first purified and characterized in 1823 by Jöns Jakob Berzelius.

Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. It is most widely distributed in dusts, sands, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. Over 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.[9]

Most silicon is used commercially without being separated, and often with little processing of the natural minerals. Such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with silica sand and gravel to make concrete for walkways, foundations, and roads. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass and many other specialty glasses. Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics.

Elemental silicon also has a large impact on the modern world economy. Most free silicon is used in the steel refining, aluminium-casting, and fine chemical industries (often to make fumed silica). Even more visibly, the relatively small portion of very highly purified silicon used in semiconductor electronics (< 10%) is essential to integrated circuits — most computers, cell phones, and modern technology depend on it. Silicon is the basis of the widely used synthetic polymers called silicones.

Silicon is an essential element in biology, although only tiny traces are required by animals.[10] However, various sea sponges and microorganisms, such as diatoms and radiolaria, secrete skeletal structures made of silica. Silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses.[11]

Silicon Spectra.jpg
Silicon Spectra.jpg



Silicon crystallizes in a diamond cubic crystal structure

Silicon is a solid at room temperature, with a melting point of 1,414 °C (2,577 °F) and a boiling point of 3,265 °C (5,909 °F). Like water, it has a greater density in a liquid state than in a solid state and it expands when it freezes, unlike most other substances. With a relatively high thermal conductivity of 149 W·m−1·K−1, silicon conducts heat well.

In its crystalline form, pure silicon has a gray color and a metallic luster. Like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a diamond cubic crystal structure with a lattice spacing of 0.5430710 nm (5.430710 Å).[12]

The outer electron orbital of silicon, like that of carbon, has four valence electrons. The 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six.

Silicon is a semiconductor. It has a negative temperature coefficient of resistance, since the number of free charge carriers increases with temperature. The electrical resistance of single crystal silicon significantly changes under the application of mechanical stress due to the piezoresistive effect.[13] Heavily boron-doped silicon is a type II superconductor with a transition temperature Tc of 0.4 K.[14]


Silizium pulver.jpg
Silicon powder

Silicon is a metalloid, readily donating or sharing its four outer electrons, and it typically forms four bonds. Like carbon, its four bonding electrons enable it to combine with many other elements or compounds to form a wide range of compounds. Unlike carbon, it can accept additional electrons and form five or six bonds in a sometimes more labile silicate form. Tetra-valent silicon is relatively inert; it reacts with halogens and dilute alkalis, but most acids (except some hyper-reactive combinations of nitric acid and hydrofluoric acid) have no effect on it.


Naturally occurring silicon is composed of three stable isotopes, 28Si (92.23%), 29Si (4.67%), and 30Si (3.10%), with 28Si being the most abundant.[15] Out of these, only 29Si is of use in NMR and EPR spectroscopy,[16] as it is the only one with a nuclear spin (I = 1/2).[17]

Twenty radioisotopes have been characterized, with the most stable being 32Si with a half-life of 170 years, and 31Si with a half-life of 157.3 minutes.[15] All of the remaining radioactive isotopes have half-lives that are less than seven seconds, and the majority of these have half-lives that are less than one tenth of a second.[15] Silicon does not have any known nuclear isomers.[15] 32Si undergoes low-energy beta decay to 32P and then stable 32S. 31Si may be produced by the neutron activation of natural silicon and is thus useful for quantitative analysis.[17]

The isotopes of silicon range in mass number from 22 to 44.[15] The most common decay mode of the isotopes with mass numbers lower than the three stable isotopes is inverse beta decay, primarily forming aluminium isotopes (13 protons) as decay products.[15] The most common decay mode for the heavier unstable isotopes is beta decay, primarily forming phosphorus isotopes (15 protons) as decay products.[15]


In 1787 Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element.[18] After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin silex, silicis for flint, and adding the "-ium" ending because he believed it was a metal.[19] In 1811, Gay-Lussac and Thénard are thought to have prepared impure amorphous silicon, through the heating of recently isolated potassium metal with silicon tetrafluoride, but they did not purify and characterize the product, nor identify it as a new element.[20] Silicon was given its present name in 1817 by Scottish chemist Thomas Thomson. He retained part of Davy's name but added "-on" because he believed that silicon was a nonmetal similar to boron and carbon.[21] In 1823, Berzelius prepared amorphous silicon using approximately the same method as Gay-Lussac (reducing potassium fluorosilicate with molten potassium metal), but purifying the product to a brown powder by repeatedly washing it.[22] As a result, he is usually given credit for the element's discovery.[23][24]

Silicon in its more common crystalline form was not prepared until 31 years later, by Deville.[25][26] By electrolyzing a mixture of sodium chloride and aluminium chloride containing approximately 10% silicon, he was able to obtain a slightly impure allotrope of silicon in 1854.[27] Later, more cost-effective methods have been developed to isolate several allotrope forms, the most recent being silicene.

Because silicon is an important element in high-technology semiconductor devices, many places in the world bear its name. For example, Santa Clara Valley in California acquired the nickname Silicon Valley since the element is the base material used in the semiconductor industry located there. Other locations have been nicknamed for similar reasons, including Silicon Forest in Oregon, Silicon Hills in Austin, Texas, Silicon Slopes in Salt Lake City, Utah, Silicon Saxony in Germany, Silicon Valley in India, Silicon Border in Mexicali, Mexico, Silicon Fen in Cambridge, England, Silicon Roundabout in London, Silicon Glen in Scotland, and Silicon Gorge in Bristol, England.


Quartz, Tibet.jpg
Quartz crystal cluster from Tibet. The naturally occurring mineral is a network solid with the formula SiO2.

Measured by mass, silicon makes up 27.7% of the Earth's crust and is the second most abundant element in the crust, with only oxygen having a greater abundance.[28] Silicon is usually found in the form of complex silicate minerals, and less often as silicon dioxide (silica, a major component of common sand). Pure silicon crystals are very rarely found in nature, but notable exceptions are crystals as large as to 0.3 mm across found during sampling gasses from Kudriavy volcano on the Kamchatka Peninsula.[29] [30]

The silicate minerals—various minerals containing silicon, oxygen and reactive metals—account for 90% of the mass of the Earth's crust. In the high temperatures prevalent in the formation of the inner solar system, silicon and oxygen readily combine, forming network solids of silicon and oxygen in compounds of low volatility. Since oxygen and silicon were the most common metals (using the astrochemical definition as anything other than hydrogen or helium) in the debris from supernova dust which formed the protoplanetary disk in the formation and evolution of the Solar System, they formed many complex silicates which accreted into larger rocky planetesimals that formed the terrestrial planets. Here, the reduced silicate mineral matrix entrapped the metals reactive enough to be oxidized (aluminium, calcium, sodium, potassium and magnesium). After loss of volatile gases, as well as carbon and sulfur by reaction with hydrogen, this silicate mixture of elements formed most of the Earth's crust.

These silicates were of relatively lower density than iron, nickel, and other metals non-reactive to oxygen, and a residuum of uncombined metallic iron and nickel sank to the planet's core, leaving a thick mantle of mostly of magnesium and iron silicates between core and crust. These are thought to be mostly silicate perovskites, followed in abundance by the magnesium/iron oxide ferropericlase.[31]

Examples of silicate minerals in the crust include those in the pyroxene, amphibole, mica, and feldspar groups. These minerals occur in clay and various types of rock such as granite and sandstone. In the crust, very pure silica occurs in different crystalline forms of quartz and opal. The crystals have the empirical formula of silicon dioxide, but do not consist of discrete silicon dioxide molecules in the manner of solid carbon dioxide. Rather, silica is structurally a network solid consisting of silicon and oxygen in three-dimensional crystals, like diamond. Less pure silica forms the natural glass obsidian. Biogenic silica occurs in the structure of diatoms, radiolaria and siliceous sponges.

Silicon is also a principal component of many meteorites, and of tektites, a mineral of possibly lunar origin, or (if Earth-derived) which has been subjected to unusual temperatures and pressures, possibly from meteorite strike.



Ferrosilicon alloy

Ferrosilicon, an iron-silicon alloy that contains varying ratios of elemental silicon and iron, accounts for about 80% of the world's production of elemental silicon, with China, the leading supplier of elemental silicon, providing 4.6 million tonnes (or 2/3 of the world output) of silicon, most of which is in the form of ferrosilicon. It is followed by Russia (610,000 t), Norway (330,000 t), Brazil (240,000 t) and the United States (170,000 t).[32] Ferrosilicon is primarily used by the iron and steel industry (see below) with primary use as alloying addition in iron or steel and for de-oxidation of steel in integrated steel plants.

Aluminium-silicon alloys (called silumin alloys) are heavily used in the aluminium alloy casting industry, where silicon is the single most important additive to aluminium to improve its casting properties. Since cast aluminium is widely used in the automobile industry, this use of silicon is thus the single largest industrial use (about 55% of the total) of "metallurgical grade" pure silicon (as this purified silicon is added to pure aluminium, whereas ferrosilicon is never purified before being added to steel).[33]

Metallurgical grade

Elemental silicon alloyed with significant quantities of other elements, usually up to 5%, is often referred to loosely as silicon metal. It makes up about 20% of the world total elemental silicon production, with less than 1 to 2% of total elemental silicon (5–10% of metallurgical grade silicon) ever purified to higher grades for use in electronics. Metallurgical grade silicon is commercially prepared by the reaction of high-purity silica with wood, charcoal, and coal in an electric arc furnace using carbon electrodes. At temperatures over 1,900 °C (3,450 °F), the carbon in the aforementioned materials and the silicon undergo the chemical reaction:

SiO2 + 2 C → Si + 2 CO

Liquid silicon collects in the bottom of the furnace, which is then drained and cooled. The silicon produced in this manner is called metallurgical grade silicon and is at least 98% pure. Using this method, silicon carbide (SiC) may also form from an excess of carbon in one or both of the following ways:

SiO2 + C → SiO + CO
SiO + 2 C → SiC + CO

However, provided the concentration of SiO2 is kept high, the silicon carbide can be eliminated by the chemical reaction:

2 SiC + SiO2 → 3 Si + 2 CO

As noted above, metallurgical grade silicon "metal" has its primary use in the aluminium casting industry to make aluminium-silicon alloy parts. The remainder (about 45%) is used by the chemical industry, where it is primarily employed to make fumed silica, with the rest used in production of other fine chemicals such as silanes and some types of silicones.[34]

As of September 2008, metallurgical grade silicon costs about US$1.45 per pound ($3.20/kg),[35] up from $0.77 per pound ($1.70/kg) in 2005.[36]

Polycrystalline silicon rod.jpg
A polycrystalline silicon rod made by the Siemens process


Today's purification processes involve the conversion of silicon into volatile liquids, such as trichlorosilane (HSiCl3) and silicon tetrachloride (SiCl4) or into the gaseous silane (SiH4). These compounds are then separated by a distillation and transformed into high-purity silicon, either by a redox reaction or by thermal decomposition. Vapor phase epitaxy of reducing silicon tetrachloride with hydrogen at approximately 1250 °C was done:

+ 2 H
→ Si + 4 HCl [37]

In the late 1950s, the American chemical company DuPont patented a method for the production of 99.99% pure silicon, using the metal zinc as a reductant to transform redistilled silicon tetrachloride into high-purity silicon by a vapor phase reaction at 900 °C. This technique, however, was plagued with practical problems, as the byproduct zinc chloride (ZnCl2) solidified and clogged lines, and was eventually abandoned in favor of more sophisticated processes.[38]

Silicon purification processes.svg
Schematic diagram of the traditional Siemens and the Fluidized bed reactor purification process.

Siemens process and alternatives

The best known technique is the so-called Siemens process. This technique does not require a reductant such as zinc, as it grows high-purity silicon crystallites directly on the surface of (pre-existing) pure silicon seed rods by a chemical decomposition that takes place when the gaseous trichlorosilane is blown over the rod's surface at 1150 °C. A common name for this type of technique is chemical vapor deposition (CVD) and produces high-purity polycrystalline silicon, also known as polysilicon. While the conventional Siemens process produces electronic grade polysilicon at typically 9N–11N purities, that is, it contains impurity levels of less than one part per billion (ppb), the modified Siemens process is a dedicated process-route for the production of silicon with purities of 6N (99.9999%) and less energy demand.[39][40][41]

A more recent alternative for the production of polysilicon is the fluidized bed reactor (FBR) manufacturing technology. Compared to the traditional Siemens process, FBR features a number of advantages that lead to cheaper polysilicon demanded by the fast-growing photovoltaic industry. Contrary to Siemens' batch process, FBR runs continuously, wasting fewer resources and requires less setup and downtime. It uses about 10 percent of the electricity consumed by a conventional rod reactor in the established Siemens process, as it does not waste energy by placing heated gas and silicon in contact with cold surfaces. In the FBR, silane (SiH4) is injected into the reactor from below and forms a fluidized bed together with the silicon seed particles that are fed from above. The gaseous silane then decomposes and deposits silicon on the seed particles. When the particles have grown to larger granules, they eventually sink to the bottom of the reactor where they are continuously withdrawn from the process.

The FBR manufacturing technology outputs polysilicon at 6N to 9N, a purity still higher than the 5N to 6N of upgraded metallurgical silicon (UMG-Si), a third technology used by the photovoltaic industry, that dispenses altogether with chemical purification, using metallurgical techniques instead. Currently most silicon for the photovoltaic market is produced by the Siemens process and only about 10 percent by the FBR technology, while UMG-Si accounts for about 2 percent. By 2020, however, IHS Technology predicts that market shares for FBR technology and UMG-Si will grow to 16.7 and 5.4 percent, respectively.[42]

The company REC is one of the leading producers of silane and polysilicon using FBR technology. The three-step chemical reaction involves (last step occurs inside the FB-reactor): (1.) 3 SiCl4 + Si + 2 H2 → 4 HSiCl3, followed by (2.) 4 HSiCl3 → 3 SiCl4 + SiH4, and (3.) SiH4 → Si + 2 H2.[43] Other precursors such as tribromosilane had been used by other companies as well.

Electronic grade

The use of silicon in semiconductor devices demands a much greater purity than afforded by metallurgical grade silicon. Very pure silicon (>99.9%) can be extracted directly from solid silica or other silicon compounds by molten salt electrolysis.[44][45] This method, known as early as 1854[46] (see also FFC Cambridge process), has the potential to directly produce 6N silicon without any carbon dioxide emission at much lower energy consumption.

6N silicon cannot be used for microelectronics. To properly control the quantum mechanical properties, the purity of the silicon must be very high. Bulk silicon wafers used at the beginning of the integrated circuit making process must first be refined to a purity of 99.9999999% often referred to as "9N" for "9 nines", a process which requires repeated applications of refining technology.

The majority of silicon crystals grown for device production are produced by the Czochralski process, (Cz-Si) It was the cheapest method available. However, single crystals grown by the Czochralski process contain impurities because the crucible containing the melt often dissolves. Historically, a number of methods have been used to produce ultra-high-purity silicon.

Early purification techniques

Early silicon purification techniques were based on the fact that if silicon is melted and re-solidified, the last parts of the mass to solidify contain most of the impurities. The earliest method of silicon purification, first described in 1919 and used on a limited basis to make radar components during World War II, involved crushing metallurgical grade silicon and then partially dissolving the silicon powder in an acid. When crushed, the silicon cracked so that the weaker impurity-rich regions were on the outside of the resulting grains of silicon. As a result, the impurity-rich silicon was the first to be dissolved when treated with acid, leaving behind a more pure product.

In zone melting, also called zone refining, the first silicon purification method to be widely used industrially, rods of metallurgical grade silicon are heated to melt at one end. Then, the heater is slowly moved down the length of the rod, keeping a small length of the rod molten as the silicon cools and re-solidifies behind it. Since most impurities tend to remain in the molten region rather than re-solidify, when the process is complete, most of the impurities in the rod will have been moved into the end that was the last to be melted. This end is then cut off and discarded, and the process repeated if a still higher purity is desired.[47]

Occupational safety and health

People can be exposed to silicon in the workplace by breathing it in, swallowing it, skin contact, and eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for silicon exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.[48]


PDMS – a silicone compound
  • Silicon forms binary compounds called silicides with many metallic elements whose properties range from reactive compounds, e.g. magnesium silicide, Mg2Si through high melting refractory compounds such as molybdenum disilicide, MoSi2.[49]
  • Silicon carbide, SiC (carborundum) is a hard, high melting solid and a well known abrasive. It may also be sintered into a type of high-strength ceramic used in armor.
  • Silane, SiH4, is a pyrophoric gas with a similar tetrahedral structure to methane, CH4. When pure, it does not react with pure water or dilute acids; however, even small amounts of alkali impurities from the laboratory glass can result in a rapid hydrolysis.[50] There is a range of catenated silicon hydrides that form a homologous series of compounds, Si
    where n = 2–8 (analogous to the alkanes). These are all readily hydrolyzed and are thermally unstable, particularly the heavier members.[51][52]
  • Disilenes contain a silicon-silicon double bond (analogous to the alkenes) and are generally highly reactive requiring large substituent groups to stabilize them.[53] A disilyne with a silicon-silicon triple bond was first isolated in 2004; although as the compound is non-linear, the bonding is dissimilar to that in alkynes.[54]
  • Tetrahalides, SiX4, are formed with all the halogens.[55] Silicon tetrachloride, for example, reacts with water, unlike its carbon analogue, carbon tetrachloride.[56] Silicon dihalides are formed by the high temperature reaction of tetrahalides and silicon; with a structure analogous to a carbene they are reactive compounds. Silicon difluoride condenses to form a polymeric compound, (SiF
  • Silicon dioxide (silica) is a high melting solid with a number of crystal forms; the most familiar of which is the mineral quartz. In crystalline quartz each silicon atom is surrounded by four oxygen atoms that bridge to other silicon atoms to form a three dimensional lattice (see below for the vitreous or glass form of pure silica). [56] Silica is soluble in water at high temperatures forming a range of compounds called monosilicic acid, Si(OH)4.[57]
  • Under the right conditions monosilicic acid readily polymerizes to form more complex silicic acids, ranging from the simplest condensate, disilicic acid (H6Si2O7) to linear, ribbon, layer and lattice structures which form the basis of the many silicate minerals and are called polysilicic acids {Six(OH)4–2x}n.[57]
  • Silica can be fused directly into glass form, as so-called fused quartz, which contains no crystalline structure. With oxides of other elements, the high temperature reaction of silicon dioxide can give a wide range of mixed glasses and glass-like network solids with various properties.[58] Examples include soda-lime glass, borosilicate glass and lead crystal glass.
  • Silicon sulfide, SiS2, is a polymeric solid (unlike its carbon analogue the liquid CS2).[59]
  • Silicon forms a nitride, Si3N4 which is a ceramic.[60] Silatranes, a group of tricyclic compounds containing five-coordinate silicon, may have physiological properties.[61]
  • Many transition metal complexes containing a metal-silicon bond are now known, which include complexes containing SiH
    ligands, SiX3 ligands, and Si(OR)3 ligands.[61]
  • Silicones are large group of polymeric compounds with an (Si-O-Si) backbone. An example is the silicone oil PDMS (polydimethylsiloxane). These polymers can be crosslinked to produce resins and elastomers.[62]
  • Many organosilicon compounds are known which contain a silicon-carbon single bond. Many of these are based on a central tetrahedral silicon atom, and some are optically active when central chirality exists. Long chain polymers containing a silicon backbone are known, such as polydimethysilylene (SiMe
    .[63] Polycarbosilane, [(SiMe
    with a backbone containing a repeating -Si-Si-C unit, is a precursor in the production of silicon carbide fibers.[63]



Building materials. Most silicon is used industrially without being separated into the element, and indeed often with comparatively little processing from natural occurrence. Over 90% of the Earth's crust is composed of silicate minerals, which are compounds of silicon and oxygen, often with metallic ions when negatively charged silicate anions require cations to balance the charge. Many of these have direct commercial uses, such as clays, silica sand and most kinds of building stone. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide). Silicates are used in making Portland cement (made mostly of calcium silicates) which is used in building mortar and modern stucco, but more importantly, combined with silica sand, and gravel (usually containing silicate minerals like granite), to make the concrete that is the basis of most of the very largest industrial building projects of the modern world. [64]

Ceramics and glass. Silica is used to make fire brick, a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example is porcelain which is based on the silicate mineral kaolinite. Traditional glass (silica-based soda-lime glass) also functions in many of the same ways, and is also used for windows and containers. In addition, specialty silica based glass fibers are used for optical fiber, as well as to produce fiberglass for structural support and glass wool for thermal insulation.

Artificial silicon compounds. Very occasional elemental silicon is found in nature, and also naturally-occurring compounds of silicon and carbon (silicon carbide) or nitrogen (silicon nitride) are found in stardust samples or meteorites in presolar grains, but the oxidizing conditions of the inner planets of the solar system make planetary silicon compounds found there mostly silicates and silica. Free silicon, or compounds of silicon in which the element is covalently attached to hydrogen, boron, or elements other than oxygen, are mostly artificially produced. They are described below.

Silicon compounds of more modern origin function as high-technology abrasives and new high-strength ceramics based upon silicon carbide. Silicon is a component of some superalloys.

Alternating silicon-oxygen chains with hydrogen attached to the remaining silicon bonds form the ubiquitous silicon-based polymeric materials known as silicones. These compounds containing silicon-oxygen and occasionally silicon-carbon bonds have the capability to act as bonding intermediates between glass and organic compounds, and to form polymers with useful properties such as impermeability to water, flexibility and resistance to chemical attack. Silicones are often used in waterproofing treatments, molding compounds, mold-release agents, mechanical seals, high temperature greases and waxes, and caulking compounds. Silicone is also sometimes used in breast implants, contact lenses, explosives and pyrotechnics.[65] Silly Putty was originally made by adding boric acid to silicone oil.[66]


Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of cementite where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of the world's use of free silicon. Silicon is an important constituent of electrical steel, modifying its resistivity and ferromagnetic properties.

The properties of silicon can be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys (silumin alloys) for aluminium part casts, mainly for use in the automotive industry. Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a eutectic mixture which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium.[33][34]


Silicon wafer with mirror finish.jpg
Silicon wafer with mirror finish

Most elemental silicon produced remains as a ferrosilicon alloy, and only about 20% is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). An estimated 15% of the world production of metallurgical grade silicon is further refined to semiconductor purity.[34] However, the economic importance of this small very high-purity fraction (especially the ~ 5% which is processed to monocrystalline silicon for integrated circuits) is disproportionately large.

Pure monocrystalline silicon is used to produce silicon wafers used in the semiconductor industry, in electronics, and in some high-cost and high-efficiency photovoltaic applications. Pure silicon is an intrinsic semiconductor, which means that unlike metals, it conducts electron holes and electrons released from atoms by heat; silicon's electrical conductivity increases with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, which greatly increase its conductivity and adjust its electrical response by controlling the number and charge (positive or negative) of activated carriers. Such control is necessary for transistors, solar cells, semiconductor detectors, and other semiconductor devices used in the computer industry and other technical applications. In silicon photonics, silicon can be used as a continuous wave Raman laser medium to produce coherent light, though it is ineffective as an everyday light source.

In common integrated circuits, a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping and insulated from each other by thin layers of silicon oxide, an insulator that is easily produced by exposing the element to oxygen under the proper conditions. Silicon has become the most popular material for both high power semiconductors and integrated circuits because it can withstand the highest temperatures and greatest electrical activity without suffering avalanche breakdown (an electron avalanche is created when heat produces free electrons and holes, which in turn pass more current, which produces more heat). In addition, the insulating oxide of silicon is not soluble in water, which gives it an advantage over germanium (an element with similar properties which can also be used in semiconductor devices) in certain fabrication techniques.[67]

Monocrystalline silicon is expensive to produce, and is usually justified only in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) used in the production of low-cost, large-area electronics in applications such as liquid crystal displays and of large-area, low-cost, thin-film solar cells. Such semiconductor grades of silicon are either slightly less pure or polycrystalline rather than monocrystalline, and are produced in comparable quatities as the monocrystalline silicon: 75,000 to 150,000 metric tons per year. The market for the lesser grade is growing more quickly than for monocrystalline silicon. By 2013, polycrystalline silicon production, used mostly in solar cells, was projected to reach 200,000 metric tons per year, while monocrystalline semiconductor grade silicon was expected to remain less than 50,000 tons/year.[34]

Mechanical watches

Since 2000, silicon has found a new use in mechanical watch movements. Several manufacturers of mechanical watch movements have incorporated silicon parts, mainly in the escapements and balance wheel regions. Silicon hair-springs are becoming more common as are silicon escapement wheels and forks. Silicon has several desirable properties when used in these contexts; It is thermally stable, shock resistant, and requires little to no lubrication. Ulysse Nardin pioneered these applications, with Omega, Breguet, Patek, Rolex, Cartier, and Damasko following.[68] Most of these parts for watch movements are manufactured by deep reactive-ion etching (DRIE).[69]

Biological role

20110123 185042 Diatom.jpg
A diatom, enclosed in a silica cell wall

Although silicon is readily available in the form of silicates, very few organisms use it directly. Diatoms, radiolaria and siliceous sponges use biogenic silica as a structural material for skeletons. In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, for example rice, need silicon for their growth.[70][71][72] There is some evidence that silicon is important to nail, hair, bone and skin health,[73] for example in studies that show that premenopausal women with higher dietary silicon intake have higher bone density, and that silicon supplementation can increase bone volume and density in patients with osteoporosis.[74] Silicon is needed for synthesis of elastin and collagen, of which the aorta contains the greatest quantity in the human body.[75] Silicic acid has also been the subject of clinical trials.

Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)."[76][77] Silicon has been shown in university and field studies to improve plant cell wall strength and structural integrity,[78] improve drought and frost resistance, decrease lodging potential, and boost the plant's natural pest and disease fighting systems.[79] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[78]

The U.S. Institute of Medicine has not confirmed that silicon is an essential nutrient for humans, so neither a Recommended Dietary Allowance nor an Adequate Intake have been established. There is also not enough information to set a Tolerable Upper Intake Level. Dietary intake is estimated at 20 to 50 mg/day, with an estimated 50% absorbed. What is absorbed is excreted in urine.[80]

See also


  1. ^ Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure Appl. Chem. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. ^ Ram, R. S.; et al. (1998). "Fourier Transform Emission Spectroscopy of the A2D–X2P Transition of SiH and SiD" (PDF). J. Mol. Spectr. 190: 341–352. PMID 9668026.
  3. ^ Eranna, Golla (2014). Crystal Growth and Evaluation of Silicon for VLSI and ULSI. CRC Press. p. 7. ISBN 978-1-4822-3281-3.
  4. ^ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  5. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  6. ^ a b c d Hopcroft, Matthew A.; Nix, William D.; Kenny, Thomas W. (2010). "What is the Young's Modulus of Silicon?". Journal of Microelectromechanical Systems. 19 (2): 229. doi:10.1109/JMEMS.2009.2039697.
  7. ^ Weeks, Mary Elvira (1932). "The discovery of the elements: XII. Other elements isolated with the aid of potassium and sodium: beryllium, boron, silicon, and aluminum". Journal of Chemical Education. 9 (8): 1386–1412. Bibcode:1932JChEd...9.1386W. doi:10.1021/ed009p1386.
  8. ^ Voronkov, M. G. (2007). "Silicon era". Russian Journal of Applied Chemistry. 80 (12): 2190. doi:10.1134/S1070427207120397.
  9. ^ Nave, R. Abundances of the Elements in the Earth's Crust, Georgia State University
  10. ^ Nielsen, Forrest H. (1984). "Ultratrace Elements in Nutrition". Annual Review of Nutrition. 4: 21–41. PMID 6087860. doi:10.1146/
  11. ^ Cutter, Elizabeth G. (1978). Plant Anatomy. Part 1 Cells and Tissues (2nd ed.). London: Edward Arnold. ISBN 0-7131-2639-6.
  12. ^ O'Mara, William C. (1990). Handbook of Semiconductor Silicon Technology. William Andrew Inc. pp. 349–352. ISBN 0-8155-1237-6.
  13. ^ Hull, Robert (1999). "Properties of crystalline silicon": 421. ISBN 978-0-85296-933-5.
  14. ^ Bustarret, E.; et al. (2006). "Superconductivity in doped cubic silicon". Nature. 444 (7118): 465–468. Bibcode:2006Natur.444..465B. PMID 17122852. doi:10.1038/nature05340.
  15. ^ a b c d e f g NNDC contributors (2008). Alejandro A. Sonzogni (Database Manager), ed. "Chart of Nuclides". Upton (NY): National Nuclear Data Center, Brookhaven National Laboratory. Retrieved 2008-09-13.
  16. ^ Jerschow, Alexej. "Interactive NMR Frequency Map". New York University. Retrieved 2011-10-20.
  17. ^ a b Greenwood and Earnshaw, p. 330
  18. ^ In his table of the elements, Lavoisier listed five "salifiable earths" (i.e., ores that could be made to react with acids to produce salts (salis = salt, in Latin): chaux (calcium oxide), magnésie (magnesia, magnesium oxide), baryte (barium sulfate), alumine (alumina, aluminium oxide), and silice (silica, silicon dioxide). About these "elements", Lavoisier speculates: "We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths. It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies. It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process." – from page 218 of: Lavoisier with Robert Kerr, trans., Elements of Chemistry, … , 4th ed. (Edinburgh, Scotland: William Creech, 1799). (The original passage appears in: Lavoisier, Traité Élémentaire de Chimie, (Paris, France: Cuchet, 1789), vol. 1, p. 174.)
  19. ^ Davy, Humphry (1808) "Electro chemical researches, on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia," Philosophical Transactions of the Royal Society [of London], 98 : 333–370. On p. 353 Davy coins the name "silicium" : "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium [silicon], alumium [aluminium], zirconium, and glucium [beryllium]."
  20. ^ Gay-Lussac and Thenard, Recherches physico-chimiques … (Paris, France: Deterville, 1811), vol. 1, pp. 313–314 ; vol. 2, pp. 55–65.
  21. ^ Thomas Thomson, A System of Chemistry in Four Volumes, 5th ed. (London, England: Baldwin, Cradock, and Joy, 1817), vol. 1. From p. 252: "The base of silica has been usually considered as a metal, and called silicium. But as there is not the smallest evidence for its metallic nature, and as it bears a close resemblance to boron and carbon, it is better to class it along with these bodies, and to give it the name of silicon."
  22. ^ See:
  23. ^ Weeks, Mary Elvira (1932). "The discovery of the elements: XII. Other elements isolated with the aid of potassium and sodium: beryllium, boron, silicon, and aluminum". Journal of Chemical Education. 9 (8): 1386–1412. Bibcode:1932JChEd...9.1386W. doi:10.1021/ed009p1386.
  24. ^ Voronkov, M. G. (2007). "Silicon era". Russian Journal of Applied Chemistry. 80 (12): 2190. doi:10.1134/S1070427207120397.
  25. ^ In 1854, Deville was trying to prepare aluminium metal from aluminium chloride that was heavily contaminated with silicon chloride. Deville used two methods to prepare aluminium: heating aluminium chloride with sodium metal in an inert atmosphere (of hydrogen); and melting aluminum chloride with sodium chloride and then electrolyzing the mixture. In both cases, pure silicon was produced: the silicon dissolved in the molten aluminium, but crystallized upon cooling. Dissolving the crude aluminum in hydrochloric acid revealed flakes of crystallized silicon. See: Henri Sainte-Claire Deville (1854) "Note sur deux procédés de préparation de l'aluminium et sur une nouvelle forme du silicium" (Note on two procedures for the preparation of aluminium and on a new form of silicon), Comptes rendus, 39 : 321–326.
    Subsequently Deville obtained crystalline silicon by heating the chloride or fluoride of silicon with sodium metal, isolating the amorphous silicon, then melting the amorphous form with salt and heating the mixture until most of the salt evaporated. See: H. Sainte-Claire Deville (1855) "Du silicium et du titane" (On silicon and titanium), Comptes rendus, 40 : 1034–1036.
  26. ^ Information on silicon – history, thermodynamic, chemical, physical and electronic properties: Retrieved on 2011-08-07.
  27. ^ Silicon: History. Retrieved on 2011-08-07.
  28. ^ Geological Survey (U.S.) (1975). Geological Survey professional paper.
  29. ^ Korzhinsky, M. A.; Tkachenko, S. I.; Shmulovich, K. I.; Steinberg, G. S. (1995). "Native AI and Si formation". Nature. 375 (6532): 544–544. ISSN 0028-0836. doi:10.1038/375544a0.
  30. ^ Cordua, Courtesy of Dr Bill (1998-01-10), English: PDF file entitled: "Silicon, Silica, Silicates and Silicone" (PDF), retrieved 2016-03-29
  31. ^ Anderson, Don (2007). New theory of the Earth. Cambridge, UK New York: Cambridge University Press. ISBN 978-0-521-84959-3.
  32. ^ "Silicon Commodities Report 2011" (PDF). USGS. Retrieved 2011-10-20.
  33. ^ a b Apelian, D. (2009) Aluminum Cast Alloys: Enabling Tools for Improved Performance. North American Die Casting Association, Wheeling, Illinois.
  34. ^ a b c d Corathers, Lisa A. 2009 Minerals Yearbook. USGS
  35. ^ "Metallurgical silicon could become a rare commodity – just how quickly that happens depends to a certain extent on the current financial crisis". Photon International. Archived from the original on July 15, 2011. Retrieved 2009-03-04.
  36. ^ "Silicon" (PDF). Retrieved 2008-02-20.
  37. ^ Morgan, D. V.; Board, K. (1991). An Introduction To Semiconductor Microtechnology (2nd ed.). Chichester, West Sussex, England: John Wiley & Sons. p. 23. ISBN 0471924784.
  38. ^ – Patents Production of silicon – Publication number US2909411 A
  39. ^ Yasuda, Kouji; Saegusa, Kunio; Okabe, Toru H. (2010). "Production of Solar-grade Silicon by Halidothermic Reduction of Silicon Tetrachloride". Metallurgical and Materials Transactions B. 42: 37. Bibcode:2011MMTB...42...37Y. doi:10.1007/s11663-010-9440-y.
  40. ^ Yasuda, Kouji; Okabe, Toru H. (2010). "Solar-grade silicon production by metallothermic reduction". JOM. 62 (12): 94. Bibcode:2010JOM....62l..94Y. doi:10.1007/s11837-010-0190-8.
  41. ^ Van Der Linden, P. C.; De Jonge, J. (2010). "The preparation of pure silicon". Recueil des Travaux Chimiques des Pays-Bas. 78 (12): 962. doi:10.1002/recl.19590781204.
  42. ^ IHS Technology Fluidized Bed Reactor Technology Stakes Its Claim in Solar Polysilicon Manufacturing, 7 May 2014
  43. ^ "Analyst silicon field trip" (PDF). March 28, 2007. Retrieved 2008-02-20.
  44. ^ Rao, Gopalakrishna M. (1980). "Electrowinning of Silicon from K2SiF6-Molten Fluoride Systems". Journal of the Electrochemical Society. 127 (9): 1940. doi:10.1149/1.2130041.
  45. ^ De Mattei, Robert C. (1981). "Electrodeposition of Silicon at Temperatures above Its Melting Point". Journal of the Electrochemical Society. 128 (8): 1712. doi:10.1149/1.2127716.
  46. ^ Deville, H. St. C. (1854). "Recherches sur les métaux, et en particulier sur l'aluminium et sur une nouvelle forme du silicium". Ann. Chim. Phys. 43: 31.
  47. ^ Siffert, Paul; Krimmel, E. F. (2004). Silicon: Evolution and future of a technology. p. 33. ISBN 978-3-540-40546-7.
  48. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Silicon". Retrieved 2015-11-21.
  49. ^ Greenwood 1997, pp. 335–337.
  50. ^ Greenwood 1997, p. 339.
  51. ^ Greenwood 1997, p. 337.
  52. ^ a b Holleman, Arnold F.; Wiberg, Nils (2007). Lehrbuch der anorganischen Chemie (102nd ed.). Berlin: de Gruyter. ISBN 3-11-017770-6.
  53. ^ Stone, F. G.; West, Robert (1996) Multiply Bonded Main Group Metals and Metalloids, Academic Press, ISBN 0-12-031139-9, p. 255
  54. ^ Sekiguchi, A.; Kinjo, R.; Ichinohe, M. (2004). "A stable compound containing a silicon-silicon triple bond". Science. 305 (5691): 1755–7. Bibcode:2004Sci...305.1755S. PMID 15375262. doi:10.1126/science.1102209.
  55. ^ Greenwood 1997, pp. 340–341.
  56. ^ a b Greenwood 1997, p. 342.
  57. ^ a b Greenwood 1997, p. 346.
  58. ^ Greenwood 1997, p. 344.
  59. ^ Greenwood 1997, pp. 359–360.
  60. ^ Greenwood 1997, p. 360.
  61. ^ a b Lickiss, Paul D. (1994). Inorganic Compounds of Silicon, in Encyclopedia of Inorganic Chemistry. John Wiley & Sons. pp. 3770–3805. ISBN 0-471-93620-0.
  62. ^ Greenwood 1997, pp. 364–365.
  63. ^ a b Mark, James. E (2005). Inorganic polymers. Oxford University Press. pp. 200–245. ISBN 0-19-513119-3.
  64. ^ Greenwood 1997, p. 356.
  65. ^ Koch, E.C.; Clement, D. (2007). "Special Materials in Pyrotechnics: VI. Silicon – An Old Fuel with New Perspectives". Propellants, Explosives, Pyrotechnics. 32 (3): 205. doi:10.1002/prep.200700021.
  66. ^ Walsh, Tim (2005). "Silly Putty". Timeless toys: classic toys and the playmakers who created them. Andrews McMeel Publishing. ISBN 978-0-7407-5571-2.
  67. ^ Semiconductors Without the Quantum Physics. Electropaedia
  68. ^ Silicon hairspring. Retrieved on 2016-12-14.
  69. ^ The Silicon revolution. (2008-08-27). Retrieved on 2016-12-14.
  70. ^ Rahman, Atta-ur-. "Silicon". Studies in Natural Products Chemistry. 35. p. 856. ISBN 978-0-444-53181-0.
  71. ^ Exley, C. (1998). "Silicon in life:A bioinorganic solution to bioorganic essentiality". Journal of Inorganic Biochemistry. 69 (3): 139–144. doi:10.1016/S0162-0134(97)10010-1.
  72. ^ Epstein, Emanuel (1999). "SILICON". Annual Review of Plant Physiology and Plant Molecular Biology. 50: 641–664. PMID 15012222. doi:10.1146/annurev.arplant.50.1.641.
  73. ^ Martin, Keith R. (2013). "Chapter 14. Silicon: The Health Benefits of a Metalloid". In Astrid Sigel; Helmut Sigel; Roland K. O. Sigel. Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. 13. Springer. pp. 451–473. doi:10.1007/978-94-007-7500-8_14.
  74. ^ Jugdaohsingh, R. (Mar–Apr 2007). "Silicon and bone health". The journal of nutrition, health and aging. 11 (2): 99–110. PMC 2658806Freely accessible. PMID 17435952.
  75. ^ Loeper, J.; Loeper, J.; Fragny, M. (1978). "The Physiological Role of the Silicon and its AntiAtheromatous Action". Biochemistry of Silicon and Related Problems: 281–296. ISBN 978-1-4613-4020-1. doi:10.1007/978-1-4613-4018-8_13.
  76. ^ "AAPFCO Board of Directors 2006 Mid-Year Meeting" (PDF). Association of American Plant Food Control Officials. Retrieved 2011-07-18.
  77. ^ Miranda, Stephen R.; Bruce Barker. "Silicon: Summary of Extraction Methods". Harsco Minerals. August 4, 2009. Retrieved 2011-07-18.
  78. ^ a b "Silicon nutrition in plants" (PDF). Plant Health Care, Inc.: 1. 12 December 2000. Retrieved 2011-07-01.
  79. ^ Prakash, Dr. N.B. (2007). "Evaluation of the calcium silicate as a source of silicon in aerobic and wet rice". University of Agricultural Science Bangalore: 1.
  80. ^ Nickel. IN: Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Copper. National Academy Press. 2001, PP. 529–532.


  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0-08-037941-9.

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