Role of hydrogen in synchrotron-radiation-stimulated evaporation of amorphous SiO2 and microcrystalline Si

Abstract

We report on the photostimulated evaporation of amorphous SiO2 and microcrystalline Si by synchrotron radiation in ultrahigh vacuum and in H2 ambients up to 0.08 Torr. For a-SiO2, the evaporation was slowed by introduction of H2, which suggests that the highly efficient decomposition process is hindered by hydrogen termination (-OH species formation). For μc-Si, the evaporation rate in ultrahigh vacuum was strongly affected by the degree of crystallization. The evaporation rate doubled with introduction of 0.08 Torr H2. Hydrogenation of the surface (SiHx species formation) slightly reduces the activation barrier for evaporation.