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Quantum confinement in closely packed arrays of Ge quantum dots (QDs) was studied for energy applications. In this work, we report an efficient tuning mechanism of the light harvesting and detection of Ge QDs. Thin films of SiGeO alloys, produced by rf-magnetron sputtering, were annealed at 600 °C in N2 to induce precipitation of small amorphous Ge QDs into the oxide matrix. Varying the Ge content, the QD size was tailored between 2 and 4 nm, as measured by high resolution transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of pure SiO2, as well as the presence of a sub-stoichiometric Ge oxide shell at the QD interface. Light absorption spectroscopy shows a clear size-dependent shift of the QD optical bandgap (Eg), between 1.4 and 2.1 eV, and was modeled using the standard effective mass approximation (EMA) or a spatially dependent …
Publication date: 
1 Apr 2015

S Cosentino, EG Barbagiovanni, I Crupi, M Miritello, G Nicotra, C Spinella, D Pacifici, S Mirabella, A Terrasi

Biblio References: 
Volume: 135 Pages: 22-28
Solar Energy Materials and Solar Cells