XPS STUDY OF AMORPHOUS AS2S3 FILMS DEPOSITED ONTO CHROMIUM LAYERS

This paper reports some XPS data on unexposed and exposed thin films o f As2S3 deposited onto chromium-coated glass substrates. We show the c hemical changes on the surface and interface of As2S3 and chromium lay ers. The chromium layers are obtained by thermal evaporation, high-fre quency sputtering and electron beam evaporation. Chemical changes of t he sample surface after laser irradiation are investigated. Exposure o f As2S3 films results in photo-induced oxidation of arsenic on the sur face and formation of As2O3. It is established that the O 1s peak area on exposed samples decreases compared to the O 1s peak area on unexpo sed ones. This is related to desorption of As2O3 from the surface of e xposed As2S3 layers. Another proof of desorption of As2O3 is the decre ase of the As 3d/S 2p normalized peak area ratio on exposed As2S3 laye rs. The sulphur content on the surface remains unchanged after exposur e of the samples, but its chemical surroundings change. An alteration of the chemical environment of As and Cr is observed at the As2S3/Cr i nterface, due to diffusion of chromium atoms through the interface int o the As2S3 layer. This results in formation of an AsxCrySz compound a t the As2S3/Cr interface, which dissolves with a lower rate. This hind ers further etching of the metal coating during photolithographic proc ess employing Cr plates with inorganic photoresist based on vacuum dep osited As2S3.