Anomalous temperature dependence of photoluminescence in GeO$_{x}$

The optical properties of GeO$_x$ film and GeO$_x$/SiO$_2$ multilayer heterostructures (with thickness of GeO$_x$ layers down to 1 nm) were studied with the use of Raman scattering and IR spectroscopy, ellipsometry and photoluminescence spectroscopy including temperature dependence of photoluminescence. The observed photoluminescence is related to defect (dangling bonds) in GeO$_x$ and interface defects for the case of GeO$_x$/SiO$_2$ multilayer heterostructures. From analysis of temperature dependence of PL intensity, it was found that rate of nonradiative transitions in GeO$_x$ film has Berthelot type, but anomalous deviations from Berthelot type temperature dependence were observed in temperature dependences of PL intensities for GeO$_x$/SiO$_2$ multilayer heterostructures.