Doping effect on the kinetics and mechanism of thermal oxidation of polycrystalline PbSe layers

We have shown that the thermal oxidation (473-773 K) of polycrystalline lead selenide layers, undoped and doped with bismuth, cadmium, tin, and chlorine, has similar effects on their electrical properties, microstructure, and phase composition. The rate of oxygen diffusion and the formation kinetics of oxide phases depend on the nature and concentration of donors in the as-deposited layers; with decreasing doping level, oxygen diffuses more rapidly. In contrast to the diffusional mechanism of oxygen incorporation and gradual microstructural changes in undoped and PbSe(Bi) layers, iodine doping gives rise to drastic structural changes, including encapsulation of PbSe grains, which are accompanied by the formation of lead oxyselenites and almost instantaneous oxygen incorporation into the surface layer of the PbSe crystallites. Moreover, iodine is shown to catalyze the formation of dielectric oxide phases, reducing the temperature of this process and resulting in high photosensitivity compared to undoped PbSe layers.