engleski

Self-assembled Ge/metal core/shell nanoparticles in alumina matrix

Core-shell structured Ge nanoparticles (quantum dots) with metallic shells (aluminium, tantalum and titanium) in an amorphous alumina matrix were investigated. The presence of metallic shells just a few atoms in thickness has shown to radically weaken oxidation of germanium but occurrence of intermixing Ge-metal or Ge-metal-O phases is implied. Greater amounts of metal in some samples caused shells to overlap forming a slab-like structure also causing loss of self- assembly. In addition, these metallic shells dramatically influence the dielectric function and absorption coefficient. Most important absorption peak energies in investigated systems are in the relevant part of solar spectrum (1 - 4.5 eV) which suggests applications of these materials in photovoltaic devices are possible. Samples with self-assembled super-lattice were created using magnetron sputtering at 300°C. Characterization methods used are Elastic recoil detection (ERDA), Transmission electron microscopy (TEM), Grazing incidence small angle X-ray scattering (GISAXS), X-ray absorption near edge structure (XANES), Raman spectroscopy and Ellipsometry.

nanoparticles ; self-assembly ; core-shell ; semiconductor ; plasmons

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