Amorphous films of the transition elements

Abstract

Thin films of the transition elements Fe, Co, Ni, Mn, and Cr have been prepared, by low temperature condensation in ultra high vacuum, 10−9 Torr. on to liquid helium cooled substrates. Resistance measurements made during film deposition and the subsequent anneal to 500°K showed a gradual decrease in resistivity arising from continuous crystallite growth for all films and rapid drops in resistivity for some films associated with an amorphous to crystalline transition. Films of iron and nickel needed several per cent of impurity to stabilise an amorphous phase, pure films being microcrystalline. All cobalt films showed the rapid drop in resistivity which was independent of substrate and evaporation rate. The impurities, necessarily present, determined the transition temperature, 38°K for the purest Co films. It is concluded that some metals can be prepared pure and in an amorphous state.