Disilane

Disilane (Si2H6) is the simplest member of the silicon-hydrogen hydride family with two silicon atoms linked by a single Si–Si bond, each bearing three hydrogen atoms. It is a colorless, highly flammable, and air-sensitive gas that is unstable in air and decomposes upon prolonged exposure to heat or oxygen.

Preparation and handling: Disilane is primarily prepared in situ for laboratory use or stored under inert conditions in specialized pressurized cylinders. Common laboratory routes involve the reduction or coupling of chlorosilane derivatives or the redistribution of silicon hydrides under reducing conditions, often in an inert solvent and at low temperatures to minimize decomposition. Disilane is typically used and handled under nitrogen or argon with rigorous exclusion of moisture and oxygen.

Reactions and properties: In the gas phase, disilane can undergo homolytic cleavage of the Si–Si bond to generate silicon-centered radicals, which participate in various gas-phase and surface reactions. It readily hydrolyzes or oxidizes upon contact with water or air, producing silicon dioxide and hydrogen gas. Compared with silane (SiH4), disilane is less stable and more challenging to handle on a routine scale.

Uses: Disilane serves mainly as a chemical vapor deposition precursor for silicon-containing films. In research and industry, it can be used to deposit silicon films or to supply silicon for doping and passivation processes in semiconductor fabrication, though silane remains more common due to greater stability and lower cost.

Safety: It is a flammable, potentially explosive gas that forms explosive mixtures with air and reacts with moisture. It must be handled with appropriate engineering controls, inert atmosphere techniques, and proper storage.

See also: Silane, Silicon hydrides, Chemical vapor deposition.