Photoluminescence in silicon rich oxide thin films under different thermal treatments

Photoluminescence (PL) was studied in silicon rich oxide (with the atomic percentage ranges of Si from 35% to 75%) thin film samples, fabricated by the plasma assisted CVD technique. A broad PL peak, blue-shifted from the bulk silicon band edge of ∼1.1 eV, was observed. In one typical sample, the PL peak intensity shows a non-monotonic temperature dependence. This non-monotonic dependence was also observed in previous work by others and attributed to an energy splitting between the excitonic singlet and triplet levels in silicon nanocrystals, a consequence of quantum confinement effect. Finally, in more than 20 samples under different thermal treatments (with the annealing temperature range from 800 °C to 1100 °C), the wavelength of PL peak was observed to be pinned between ∼900 and ∼1000 nm, independent of thermal budget. This pinning effect, we believe, is probably due to the formation of oxygen-related interface states.