Silicides are binary compounds of silicon with other more electropositive elements. Chemical bonds in silicides may exhibit primarily covalent or primarily ionic characteristics, depending on the electronegativity of participating elements.
Silicides of many transition metals and all non-transition metals except beryllium have been described; mercury, thallium, bismuth, and lead are nonmiscible with liquid silicon. Transition metal silicides are usually inert to all aqueous solutions with the exception of hydrofluoric acid, but they can react with more aggressive agents such as potassium hydroxide or halogen gases when subjected to extremely high temperatures.
Silicides play important roles in the field of advanced technology. Thin films of metal silicides are integral to the integrated circuits of semiconductor and microelectronics devices, the most common including CoSi2, NiSi2, WSi2, MoSi2, TaSi2, TiSi2., and PtSi, a superconductor and Schottky barrier used in infrared detection and Schottky contacts. These materials are typically synthesized via sputtering deposition of the metal onto a high purity silicon wafer. Alkali metal silicides like sodium silicide generate pure hydrogen when reacted with water or water-based solutions, making them a potentially viableas a clean, sustainable source of hydrogen for fuel cells. Niobium silicide was used to create the first functional printed diode that worked up to the GHz range, and a novel lithium borosilicide (LiBSi2) has been investigated as a promising anode material for lithium-ion batteries that could increase cell capacity.