Investigation of Quantum Confinement Effects on Tin Quantum Dot Materials for Photovoltaic Applications

  • Mr Yong Heng So, University of New South Wales, Australia
  • Dr Shujuan Huang, University of New South Wales, Australia
  • Dr Gavin Conibeer, University of New South Wales, Australia
  • Dr Eunchel Cho, University of New South Wales, Australia
  • Dr Martin Green, University of New South Wales, Australia

    • Objective
    Quantum dot superlattices can be used to engineer the band gap of nanostructure material. This can be useful to tailor the band gap of photovoltaic devices, for instance for low cost tandem solar cells. Tin nanostructure materials have attracted growing interest recently due to low process temperatures and possible band gap flexibility. Previous works on fabrication of tin (Sn) quantum dots (QDs) in silicon oxide showed significant oxidation of the Sn. Recently, silicon nitride (Si3N4) has been used as a matrix to avoid this problem. Characterisation of these structures has shown that small Sn QDs were successfully grown in the Si3N4 matrix. In the current works, investigation of smaller Sn QD sizes in Si3N4 multilayer structures is carried out to study the effects of quantum confinement on the optoelectronic properties.

    Method
    Sn-rich silicon nitride films were prepared by magnetron co-sputtering from Sn and Si3N4 targets. Multilayer structures were prepared by depositing alternating layers of Sn-rich and nominally stoichiometric Si3N4. Characterisation of size, shape and phase separation as well as crystalline properties of Sn QDs formed in the Si3N4 matrix was carried out using TEM and X-ray diffraction (XRD), respectively. Also, optical absorption was measured by UV-visible-NIR spectrophotometer and Photoluminescene (PL) was used as a measure as to whether quantum confinement opens up a band gap in the Sn QD materials.

    Results&Conclusions
    TEM (Fig.1) and XRD measurements show the formation of crystallised Sn QDs in Si3N4. Other characterisation studies on Sn QDs in Si3N4 matrix will be performed and discussed.