Size evolution and photoluminescence of silicon nanocrystallites in evaporated SiOx thin films upon thermal processing

Silicon suboxide thin films have been fabricated by physical vapor deposition of silicon monoxide in vacuum at controlled oxygen partial pressure. These films undergo a phase separation into silicon- and oxygen-enriched regions upon thermal processing. At temperatures around 900 °C, the onset of Si nanocrystallite formation is observed, regardless of film stoichiometry. With increasing initial oxygen content of the films, the mean size of created nanocrystallites decreases whereas the corresponding photoluminescence emission blueshifts. The photoluminescence intensity increases with increasing annealing temperature up to 1050 °C. Upon resonant excitation at low temperatures, the photoluminescence exhibits phonon replica signature. Therefore, the emission may be attributed to excitonic recombination in the nanocrystallites.