STUDY OF ANNEALED AMORPHOUS HYDROGENATED FILMS BY ELASTIC RECOIL DETECTION ANALYSIS

Hydrogen out-diffusion in amorphous hydrogenated films, a-Ge:D, a-C:H and a-C:H(N) films, was studied by using elastic recoil detection analysis (ERDA). The a-Ge:D films were deposited onto Si substrates at 210-degrees-C by rf-sputtering in an atmosphere of argon and deuterium. The a-C:H and a-C:H(N) films produced by plasma decomposition of a methane-nitrogen mixture, were deposited onto Si substrates at room-temperature. The a-Ge:D samples were annealed in nitrogen atmosphere at temperatures between 200 and 400-degrees-C and the carbon films in a vacuum furnace, with the temperature ranging from 300 to 700-degrees-C. The total hydrogen (deuterium) content and the concentration depth-profiles were determined by ERDA using helium beams of 2.2 and 3.0 MeV for hydrogen and deuterium profiles, respectively. Two kinds of hydrogen motion coexist in a-Ge:D films: a fast one, probably due to the presence of a network of interconnected voids, and a slower one, due to the dispersive-like diffusion of atomic deuterium in the amorphous skeleton. In a-C:H and a-C:H(N) films only the fast process was observed. A correlation between hydrogen loss and structural modifications of annealed carbon films was also made.