Si nanoparticle interfaces in Si/SiO2 solar cell materials
  Novel solar cell materials consisting of Si nanoparticles embedded in SiO2 layers have been studied using positron annihilation spectroscopy in Doppler broadening mode, and photoluminescence. Two positron-trapping interface states are observed after high temperature annealing at 1100{\deg}C. One of the states is attributed to the (SiO2/Si bulk) interface and the other to the interface between the Si nanoparticles and SiO2. A small reduction in positron trapping into these states is observed after annealing the samples in N2 atmosphere with 5% H2. Enhanced photoluminescence is also observed from the samples following this annealing step. 
S. Kilpelainen, Y.-W. Lu, F. Tuomisto, J. Slotte and A. Nylandsted   Larsen
cond-mat.mtrl-sci