Keywords: ion beam synthesis, Ge nanostructure, phase separation, semiconductor nanostructures, electronic excitation, nanotechnology, germanium dioxide
Formation of semiconductor nanostructures by dense electronic excitation
Formation of controlled semiconductor nanostructures on and near the surface region using dense electronic excitation produced by high energy heavy ions has been reviewed. Various parameters of the energetic ion beams such as energy, species and beam current can be controlled to have desired size. Results of new initiatives on production of Ge nanostructures of desired size by high-energy heavy ions are discussed. GeOx films were irradiated by 100 MeV gold (Au) ions. Formation of Ge nanostructures was studied by various techniques like micro Raman, Fourier transform infrared spectroscopy (FTIR), glancing incident X-ray diffraction (GIXRD), transmission electron microscopy (TEM), high resolution electron microscopy (HREM), atomic force microscopy (AFM), elastic recoil detection analysis (ERDA), magnetic force microscopy (MFM) and magnetisation measurements. Development of Ge nanostructures is explained on the basis of phase separation of GeOx and controlled crystallisation of Ge in the nanometre scale taking place around the trajectory of the swift heavy ion. Nanostructures are formed in a controlled manner by dense electronic excitation due to melting and subsequent fast cooling of the region along the trajectories of the energetic ions.