(Invited) Exploring the Potential of Si and Ge Amorphous Nanostructures for Photonic Applications

Abstract

The design and synthesis of nanocomposite thin films based on Si or Ge amorphous nanostructures embedded in amorphous aluminum oxide (a- Al2O3) has been investigated with the aim to achieve a controlled optical response. The films have been prepared using pulsed laser deposition at room temperature in vacuum. The formation of the nanostructures is achieved in-situ by alternated ablation of the semiconductor (Si or Ge) and a- Al2O3 targets, with no post-deposition annealing processes. The quantum confinement properties of the a-Si:a- Al2O3 and a-Ge:a- Al2O3 nanocomposite films have been studied through their optical response from the near-UV to the near-IR. A clear absorption edge, which is linked to the optical band-gap of the semiconductor nanostructures, is observed. This optical band-gap is red-shifted as the semiconductor content in the film increases and depends on the nature of the semiconductor. It shifts in the 2 to 3 eV range for Si and from 1 to 4 eV for Ge. Finally the potential of these nanostructures for the sensitization of Er ions is disclosed. In particular it will be shown how structures with enhanced response can be designed and thus optimized emission from a single layer can be achieved.