Silicide


Silicide

A silicide is a compound that has silicon with more electropositive elements.

Silicon is more electropositive than carbon. Silicides are structurally closer to borides than to carbides.

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 or ionic. Silicides of all non-transition metals, with exception of beryllium, have been described.

Mercury, thallium, bismuth, 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: Uranium3Si2, Hafnium and Thorium silicides
* Si4 tetrahedra: PotassiumSi, RubidiumSi, CaesiumSi
* Sin chains: USi, (Ti, Zr, Hf, Th, Ce, Pu)Si, CaSi, SrSi, YSi
* Planar hexagonal graphite-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 silicides are, in contrast, usually inert to aqueous solutions of everything with exception of hydrofluoric acid; however, they react with more aggressive agents, eg. melted potassium hydroxide, or fluorine and chlorine when red-hot.

Silicide prepared by a self-aligned process is called salicide. 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, Mg2Si
* Platinum silicide, PtSi
* Titanium silicide, TiSi2
* Tungsten silicide, WSi2See for a list.

References


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Look at other dictionaries:

  • Silicide — sind binäre metallische Verbindungen des Siliciums und werden meist den intermetallischen Verbindungen zugerechnet. Sie sind Halbleiter, weisen Metallglanz auf und kristallieren in definierten Strukturen aus. Es sind die Silicide vieler Metalle… …   Deutsch Wikipedia

  • Silicide — Silicide,   Singular Silicid das, (e)s, aus Silicium und einem Metall bestehende Verbindungen, die meist metallisch aussehen, gut kristallisieren und, mit Ausnahme der Alkali und Erdalkalisilicide, gegen Wasser und verdünnte Säuren beständig sind …   Universal-Lexikon

  • Silicide — Sil i*cide, n. (Chem.) A binary compound of silicon, or one regarded as binary. [R.] [1913 Webster] {Hydrogen silicide} (Chem.), a colorless, spontaneously inflammable gas, {SiH4}, produced artifically from silicon, and analogous to methane;… …   The Collaborative International Dictionary of English

  • silicide — [silisid] n. m. ÉTYM. 1871; de silice, et ide. ❖ ♦ Chim. || Les silicides : famille de corps comprenant la silice et ses combinaisons. Au sing. || Un silicide : un corps de cette famille …   Encyclopédie Universelle

  • Silicide — Silicide, die Verbindungen des Silicium mit Metallen und mit Kohlenstoff. Die letztere nennt man gewöhnlich Siliciumkarbid. (Rathgen) Moye …   Lexikon der gesamten Technik

  • silicide — [sil′i sīd΄] n. a binary compound of silicon and another element, usually a metal …   English World dictionary

  • silicide — silicidas statusas T sritis chemija formulė Formulę žr. priede. priedas( ai) Grafinis formatas atitikmenys: angl. silicide rus. силицид …   Chemijos terminų aiškinamasis žodynas

  • silicide — noun Etymology: International Scientific Vocabulary silicon + ide Date: circa 1868 a binary compound of silicon with a more electropositive element or group …   New Collegiate Dictionary

  • silicide — /sil euh suyd , sid/, n. Chem. a compound of two elements, one of which is silicon. [1865 70; SILIC(ON) + IDE] * * * …   Universalium

  • silicide — noun Any compound of silicon with a more electropositive element …   Wiktionary


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