Growing metal nanowires

A method is disclosed for growing metal (including semiconductor metal) nanowires from a film deposited on a substrate. In an illustrative embodiment tin and silicon are co-deposited, such as by sputtering, on a silicon substrate at, for example, ambient temperature. The deposited tin and silicon do not mix and the film has a tin phase dispersed in a higher melting, lower coefficient of thermal expansion, silicon phase. Upon heating, the tin expands against the silicon and expels small tin wires from the upper surface of the film. Other metal or metal alloy wires may be formed in a like manner using a matrix material and substrate in film deposition that don't mix with the metal composition and, when heated, force the expanding metal to extrude from the film surface as small diameter wires.