Effects of hydrogen in the annealing environment on photoluminescence fromSi nanoparticles in SiO2

The role of hydrogen in enhancing the photoluminescence (PL) yield observed from Si nanocrystals embedded in SiO2 has been studied. SiO2 thermal oxide s and bulk fused silica samples have been implanted with Si and subsequentl y annealed in various ambients including hydrogen or deuterium forming gase s (Ar+4%H-2 or Ar+4%D-2) or pure Ar. Results are presented for annealing at temperatures between 200 and 1100 degrees C. Depth and concentration profi les of H and D at various stages of processing have been measured using ela stic recoil detection. Hydrogen or deuterium is observed in the bulk after annealing in forming gas but not after high temperature (1100 degrees C) an neals in Ar. The presence of hydrogen dramatically increases the broad PL b and centered in the near infrared after annealing at 1100 degrees C but has almost no effect on the PL spectral distribution. Hydrogen is found to sel ectively trap in the region where Si nanocrystals are formed, consistent wi th a model of H passivating surface states at the Si/SiO2 interface that le ads to enhanced PL. The thermal stability of the trapped H and the PL yield observed after a high temperature anneal have been studied. The hydrogen c oncentration and PL yield are unchanged for subsequent anneals up to 400 de grees C. However, above 400 degrees C the PL decreases and a more complicat ed H chemistry is evident. Similar concentrations of H or D are trapped aft er annealing in H-2 or D-2 forming gas; however, no differences in the PL y ield or spectral distribution are observed, indicating that the electronic transitions resulting in luminescence are not dependent on the mass of the hydrogen species. (C) 1999 American Institute of Physics. [S0021-8979(99)07 913-X].