Patrick R. Wilson

Effect of thermal treatment on the growth, structure and luminescence of nitride-passivated silicon nanoclusters

Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.

The Influence of Structural Ordering on Luminescence from Nitride- and Oxynitride-Passivated Silicon Nanoclusters

Luminescent silicon nanoclusters have been formed in silicon-rich silicon nitride and silicon-rich silicon oxynitride films grown using inductively coupled plasma chemical vapour deposition. The luminescent properties and electronic structure of the films have been investigated through ultraviolet-excited photoluminescence and synchrotron-based X-ray absorption spectroscopy experiments at the Si K- and L3,2-edges, respectively. In the silicon-rich silicon nitride films, luminescence in the visible was observed from quantum confinement effects and inter-bandgap defect levels while X-ray absorption spectroscopy indicates a structural reordering of the silicon nanoclusters and nitride host matrix with increased silicon nanocluster phase separation, occurring at lower annealing temperatures in more silicon-rich films. Luminescence from the silicon-rich silicon oxynitride films appeared to be defect-related and only the silicon oxide and nitride host matrices exhibited structural reordering when annealed, while there was no change in the structure of the silicon nanoclusters.

X-ray spectroscopy studies of luminescent Si-based materials

X-ray based spectroscopies have been used to study nanocluster formation and luminescence in silicon oxynitride-based materials. For a luminescent Ce-doped silicon oxide details of the local chemical environment of the Ce atoms has been obtained.