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Silicide
 
 
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A silicide is a compound that has silicon
Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
 with more electropositive elements.

Silicon is more electropositive than carbon. Silicides are structurally closer to boride
Boride

In chemistry a boride is a chemical compound between boron and a less electronegativity element. This is a very large group of compounds that are generally high melting and are not ionic in nature....
s than to carbide
Carbide

In chemistry, a carbide is a compound composed of carbon and a less electronegativity element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides....
s.

Similar to borides and carbides, the composition of silicides cannot be easily specified as covalent molecules. The chemical bonds in silicides range from conductive metal-like structures to covalent
Covalent bond

A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds....
 or ionic
Ionic bond

An ionic bond is a type of chemical bond that involves a metal and a non-metal ions through electrostatic attraction. In short, it is a bond formed by the attraction between two oppositely charged ions....
. Silicides of all non-transition metals, with exception of beryllium
Beryllium

Beryllium is a chemical element with the symbol Be and atomic number 4.A Bivalent element, beryllium is found naturally only combined with other elements in minerals....
, have been described.

Mercury
Mercury (element)

Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
, thallium
Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air....
, bismuth
Bismuth

Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....
, and lead are nonmiscible with liquid silicon.

Silicon atoms in silicides can have many possible organizations:

Group 1 and 2 silicides e.g.






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Encyclopedia


A silicide is a compound that has silicon
Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
 with more electropositive elements.

Silicon is more electropositive than carbon. Silicides are structurally closer to boride
Boride

In chemistry a boride is a chemical compound between boron and a less electronegativity element. This is a very large group of compounds that are generally high melting and are not ionic in nature....
s than to carbide
Carbide

In chemistry, a carbide is a compound composed of carbon and a less electronegativity element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides....
s.

Similar to borides and carbides, the composition of silicides cannot be easily specified as covalent molecules. The chemical bonds in silicides range from conductive metal-like structures to covalent
Covalent bond

A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds....
 or ionic
Ionic bond

An ionic bond is a type of chemical bond that involves a metal and a non-metal ions through electrostatic attraction. In short, it is a bond formed by the attraction between two oppositely charged ions....
. Silicides of all non-transition metals, with exception of beryllium
Beryllium

Beryllium is a chemical element with the symbol Be and atomic number 4.A Bivalent element, beryllium is found naturally only combined with other elements in minerals....
, have been described.

Mercury
Mercury (element)

Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
, thallium
Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air....
, bismuth
Bismuth

Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....
, and lead are nonmiscible with liquid silicon.

Silicon atoms in silicides can have many possible organizations:
  • Isolated silicon atoms: electrically conductive Cu5Si, (V,Cr,Mn)3Si, Fe3Si, Mn3Si, and nonconductive (Mg,Ge,Sn,Pb)2Si, (Ca,Ru,Ce,Rh,Ir,Ni)2Si)
  • Si2 pairs: 3Si2, and silicides
  • Si4 tetrahedra
    Tetrahedron

    A tetrahedron is a polyhedron composed of four triangle faces, three of which meet at each vertex . A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids....
    : Si, Si, Si
  • Sin chains: USi, (Ti, Zr, Hf, Th, Ce, Pu)Si, CaSi, SrSi, YSi
  • Planar hexagonal graphite
    Graphite

    The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Greek language ??afe?? : "to draw/write", for its use in pencils, where it is commonly called lead, as distinguished from the actual metallic element lead....
    -like Si layers: β-USi2, silicides of other lanthanoids and actinoids
  • Corrugated hexagonal Si layers: CaSi2
  • Open three-dimensional Si skeletons: SrSi2, ThSi2, α-USi2


Group 1 and 2 silicides e.g. Na2Si and Ca2Si react with water to yielding hydrogen and/or silanes. The transition metal
Transition metal

In chemistry, the term transition metal has two possible meanings:*It commonly refers to any element in the d-block of the periodic table, including the group 12 element elements zinc, cadmium and Mercury ....
 silicides are, in contrast, usually inert to aqueous solutions of everything with exception of hydrofluoric acid
Hydrofluoric acid

Hydrofluoric acid is a solution of hydrogen fluoride in water. While it is extremely corrosive and dangerous to handle, it is technically a weak acid....
; however, they react with more aggressive agents, eg. melted potassium hydroxide
Potassium hydroxide

Potassium hydroxide is the inorganic compound with the formula potassiumhydroxide. Along with sodium hydroxide, this colourless solid is a prototypical "strong base"....
, or fluorine
Fluorine

Fluorine is the chemical element with the symbol F and atomic number 9. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F2 molecule....
 and chlorine
Chlorine

Chlorine...
 when red-hot.

Silicide prepared by a self-aligned process is called salicide
Salicide

The term salicide refers to a technology used in the microelectronics industry used to form electrical contacts between the semiconductor device and the supporting interconnect structure....
. This is a process in which silicide contacts are formed only in those areas in which deposited metal (which after annealing becomes a metal component of the silicide) is in direct contact with silicon, hence, the process is self-aligned. It is commonly implemented in MOS/CMOS processes for ohmic contacts of the source, drain, and poly-Si gate.

Examples


  • nickel silicide, NiSi
  • sodium silicide, Na2Si
  • magnesium silicide
    Magnesium silicide

    Magnesium silicide, Mg2Si, is an inorganic compound consisting of magnesium and silicon. Silicon dioxide, SiO2, found in sand and glass, when heated with magnesium forms magnesium silicide....
    , Mg2Si
  • Platinum silicide
    Platinum silicide

    Platinum silicide is a semiconductor material used in infrared detectors. It is used in detectors for infrared astronomy.Platinum silicide is capable of operating at 1?5 ?m wavelength range....
    , PtSi
  • Titanium silicide, TiSi2
  • Tungsten silicide, WSi2
See category for a list.