Silylidyne is a chemical substance occurring as a molecule found in stars and probably existing in interstellar space, or as a
monolayer
A monolayer is a single, closely packed layer of entities, commonly atoms or molecules.
Monolayers can also be made out of cells. ''Self-assembled monolayers'' form spontaneously on surfaces. Monolayers of layered crystals like graphene and molyb ...
on the surface of solid
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
. The SiH molecule is a
radical
Radical (from Latin: ', root) may refer to:
Politics and ideology Politics
*Classical radicalism, the Radical Movement that began in late 18th century Britain and spread to continental Europe and Latin America in the 19th century
*Radical politics ...
, and can be made experimentally by striking an
electric arc
An electric arc (or arc discharge) is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma ( ...
to silicon on a low pressure
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
gas.
Surface
As a surface layer, silicon hydrides form when the silicon is cleaned with hydrofluoric acid. These hydrides decompose to SiH when heated to 750 K.
Other ways to coat a silicon surface in hydrogen is via reaction with
atomic hydrogen
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral hydrogen atom contains a single positively charged proton in the nucleus, and a single negatively charged electron bound to the nucleus by the Coulomb for ...
, or hot
silane
Silane (Silicane) is an inorganic compound with chemical formula . It is a colorless, pyrophoric gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental ...
.
[ A (111) crystal face will become covered in the pure monohydride, but other faces on a silicon crystal will also have the dihydride and trihydride groups.]
Group
The silylidyne group, not to be confused with silylidyne, is a ≡SiH group that is bonded with a triple bond. The hydrogen can be substituted by other groups to make a more generic family of silylidynes. It is known as a ligand on molybdenum.
Natural occurrence
Silylidyne in space was first noticed in sun spot
Sun SPOT (Sun Small Programmable Object Technology) was a sensor node for a wireless sensor network developed by Sun Microsystems announced in 2007. The device used the IEEE 802.15.4 standard for its networking, and unlike other available sen ...
s in 1933. Later on it was found on the solar disk, photosphere, and in cool stars. Mira variable stars of type M or S may have emission lines of SiH. In even cooler brown dwarf
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...
s and planets, SiH is not found, but instead silicon takes form as silicon monoxide
Silicon monoxide is the chemical compound with the formula SiO where silicon is present in the oxidation state +2. In the vapour phase, it is a diatomic molecule.
It has been detected in stellar objects and has been described as the most common o ...
at low pressures, and SiH4 at high pressures. Minute amounts of SiH as a transient species may be found in these bodies as SiO and SiH4 react with water.
Properties
The Si-H bond strength is 80 kcal/mol.[
]
Spectrum
The most prominent spectral band is due to A2Δ → X2Π transitions. Higher level excited states are the B2Σ− and C2Σ+, D2Δ, E2Σ+.[
The life time of the molecules in the A state is 530 nanoseconds. They decay to the X ground state.][
]
References
{{Reflist
Silanes