Thin films of Au-Pd of varying composition were formed by electron beam physical vapor deposition. They were characterized and their application as optical hydrogen sensors was studied. In addition, parameters of sensing performance such as Pd deficiency during deposition, grain size, compositional homogeneity, and the appearance of a natural buffer layer, were examined. Following deposition, Au-Pd films exhibited high atomic intermixing, and a PdO(x) buffer layer formed spontaneously. This layer makes it possible to increase film thickness, which improves the intensity of the detecting signal. Accordingly, the suggested deposition method may optimize recent efforts to use Au20 wt.%-Pd thin alloy film in optical hydrogen sensors. (C) 2010 Elsevier B.V. All rights reserved.