The influence of oxygen on the thermal mixing of Cr and Gd_xO_y thin films

Abstract

Thin films of Cr and Gd oxide were sequentially deposited on Kapton H polyimide and heat treated in vacuum or air at 550-673 K. The interactions between the layers was followed with Auger electron spectroscopy and Rutherford back-scattering spectrometry. Heating caused the Cr oxide thickness to grow as a function of thermal exposure. No intermixing occurred between the Cr and Gd,O, layers until the presence of 0 in the Cr layer near the interface. Rapid diffusion of Cr oxide into the Gd oxide layer then occurred. The Gd/O Auger signal ratio increased on heating when the Cr film thickness was small, but remained unaffected with thicker Cr films. There was no diffusion of Gd into the Cr overlayer. Diffusion of Gd,O, into the polyimide was observed. A thin Cr underlayer acted as a barrier to such diffusion, but possibly only till its oxidation. Irrespective of the compositional changes, heating increased the tensile stress of the films; they also showed a greater susceptibility to tearing. The films became progressively darker, eventually turning chocolate brown. They retained their metallic lustre much longer, until the oxidation of the Cr film.