Radiative recombination in Ge+-implanted SiO2 films annealed under hydrostatic pressure

Photoluminescence (PL) spectra and PL excitation spectra were recorded at room temperature from SiO₂ films implanted with Ge⁺ ions and annealed at temperature T _a =450–1100°C under hydrostatic pressure P=12 kbar. The emergence of features in the violet and green bands of the PL and PL excitation spectra correlates with the formation of hydrostatically strained Ge nanocrystals. The shift of the PL bands to higher energies, which occurs as the annealing temperature is raised to T _a ≥800°C, can be attributed to a shift of the energy levels related to the radiative recombination centers, which is caused by the increasing deformation potential. The observed PL is accounted for by the enhanced probability of direct radiative transitions in Ge nanocrystals with an X-like conduction band.