Resistance stabilization of Ni–Cr films by surface oxide formation

Abstract

An investigation has been made of the resistivity and temperature coefficient of resistivity of Ni–Cr thin films deposited under carefully controlled conditions in ultrahigh vacuum. Auger depth profiling has been used to monitor the films, quantification of the Auger data being achieved both by the use of bulk alloy standards and by Rutherford backscattering. This paper deals specifically with the effects of residual gas on the resistance of the film and describes how this may be stabilized by the formation of a surface oxide. After stabilization the films have resistivities and temperature coefficients of resistivity which are indistinguishable from bulk samples of the same composition. Auger data has shown that the skin is predominately chromium oxide with a thickness in the region of two monolayers, this figure being supported by the percentage change of resistance on oxidation.