Temperature dependences of photoluminescence spectra of single-crystal Ca2GeO4:Cr4+ films

The temperature dependence of photoluminescence spectra in the wavelength range of 1.1-1.4 mum was measured at temperatures of 77-573 K in single-crystal Ca2GeO4:Cr+ films deposited onto the (110) surface of Ca2GeO4 single crystal and studied. The analysis of the spectra was based on the concept of interaction of emitting-center electrons with vibrations excited in the film. The results suggested that interaction of electrons with vibrations of the crystal lattice was suppressed and interaction with vibrations of the emitting center were dominant. The experimentally observed shift of the zero-phonon line in the spectra of the film in reference to that in the spectra of bulk single crystals is attributed to an increase in the symmetry of the oxygen tetrahedron in the olivine crystal structure; this increase is believed to be caused by the presence of defects in the films. (C) 2002 MAIK "Nauka / Interperiodica".