The Gas Content, Crystal Structure, and Hydrogen Absorption of Sputtered Nickel Films

Abstract

With the use of a special deposition tube which allowed the withdrawal of the cathode without altering vacuum conditions, films of nickel have been sputtered in residual atmospheres of hydrogen, helium, nitrogen, and argon, and their gas content investigated. This is large, though in general not reaching one molecule per atom of metal. Upon heating, the gas is emitted copiously at 300°-400°C, which is just the baking temperature range for which such films become magnetic and also much better conducting. As permeability is supposed to be a rapid inverse function of atomic distance it seems probable that the gas, by keeping the atoms apart, is primarily responsible for the abnormal magnetic and other properties of such films, although it is impossible to separate this effect entirely from the factor of crystal structure. Resistance measurements made during baking on a series of sputtered and evaporated films indicate that the evaporated film contains much less gas than the sputtered even when produced in the same gas pressure. This may be explained on the basis of the excitation or activation of the gas during the sputtering process, which promotes its occlusion—sometimes as a compound with the metal.