Formation of Nanocomposites by Oxidizing Annealing of SiOx and SiOxErF Films: Ellipsometry and FTIR Analysis

摘要

The structural-phase transformations induced by air annealing of SiOx and SiOx < Er,F > films were studied by the combined use of infrared spectroscopy and ellipsometry. The films were prepared using vacuum evaporation of SiO powder and co-evaporation of SiO and ErF3 powders. The annealing took place at moderate temperatures (750 and 1000 °C). It was found that the micro- and macrostructure of the annealed films is similar to the structure of the Si–SiOx nanocomposites obtained by annealing SiOx in vacuum or inert atmosphere and subjected to post-annealing in oxidizing atmosphere. This proves that the phase separation in the non-stoichiometric SiOx films proceeds much faster than their oxidation. The results of the work point at a possibility to simplify the annealing technology by replacing the two-step annealing with one-step in the oxygen-containing environment while maintaining the positive effects. The differences in the structure of the nanocomposites obtained by annealing the SiOx and SiOx < Er,F > films are explained by the action of Er centers as the promoters for SiOx disproportionation, as well as the enhanced action of F on the processes of disorder-to-order transition and crystallization in amorphous silicon.