Onset of electrical conduction in Pt and Ni films

Publisher Website
Google Scholar
Abstract
The resistance Rf of Pt and Ni films has been measured during deposition (by ion‐beam sputtering) for different deposition rates r and substrate temperatures TS (300≤TS≤575 K). At the onset of deposition (the nucleation stage) Rf varies only slowly with deposition time T and oscillations occur in Rf vs T which are damped at the larger values of r,TS. Over the second stage, during which the metallic nuclei grow in size, Rf decreases over many orders of magnitude and the Rf versus fractional coverage x behavior is described by percolation‐type equations around a critical thickness tc. The film thickness tmin (=rTmin) at which the film becomes continuous (x=1) is identified with the minimum in the Rt2 vs t graph. For t≳tmin the Rf vs t behavior is described by surface and grain‐boundary scattering equations, the derived values of grain size are related to TS, r, and compared with transmission electron microscope observations. Postdeposition temperature cycling measurements on films deposited at TS=300 K show predominantly thermally activated conduction for t<t0 (tc<t0<tmin). Rf is decreased by annealing, except in the case of Pt (tt≤1.5 nm), due to agglomeration and the formation of conducting links which also change the temperature coefficient of resistance.