Continuously tunable photoluminescence from Si+-implanted and thermally annealed SiO2 films

Efficient visible room-temperature photoluminescence, that can be continuously tuned from the blue (2.8 eV) to the red in successive annealing steps, is observed for Si+-implanted thermal oxide layers on (100) Si wafers. It is shown that the electron spin resonance signal is reduced by the annealing while the luminescence increases in intensity. From this observation we conclude that the red band of the tunable luminescence in the 1.9 eV range is not caused by a paramagnetic point defect. The observation of Si-crystallites in transmission electron microscopy leads us to argue that the red shift in the photoluminescence is the same size-related effect known from porous Si.