Improved luminescence intensity and stability of nanocrystalline silicon due to the passivation of nonluminescent states

Luminescence intensity and stability of nanocrystalline silicon (nc-Si) passivated with oxygen and hydrogen atoms have been studied by using electron-spin resonance and photoluminescence measurements. The oxygen-passivated nc-Si with low-density Pce′ centers (luminescent states) and high-density Pb centers (nonluminescent states) exhibited weak red luminescence. When the nc-Si surface was passivated with hydrogen atoms in addition to oxygen atoms using a hydrofluoric acid solution treatment, the intensity of red luminescence increased more than one order of magnitude with an increase of Pce′ centers and reduction of Pb centers on the surface. Furthermore, the red luminescence of nc-Si was very stable even after aging beyond one year, owing to the existence of only Pce′ centers and the absence of Pb centers. These results are a strong indication that the improved luminescence intensity and stability is due to the hydrogen and oxygen passivation of nonluminescent states.