Optical properties of Ge-oxygen deficient centers embedded in silica films

The emission features of Ge-oxygen deficient centers in a 100 nm thick Ge-doped silica films were investigated by looking at the photoluminescence spectra and time decay under synchrotron radiation excitation in the 10\u2013300 K temperature range. These centers exhibit two luminescence bands centered at 4.3 eV and 3.2 eV associated with the de-excitation from singlet (S1) and triplet (T1) states, respectively, that are linked by an intersystem crossing process. The comparison with results obtained in a bulk Ge-doped silica sample shows that the efficiency of the intersystem crossing process depends on the properties of the matrix embedding the Ge-oxygen deficient centers, being more effective in the film than in the bulk counterpart