Isoelectronic Series of Oxygen Deficient Centers in Silica: Experimental Estimation of Homogeneous and Inhomogeneous Spectral Widths

We report nanosecond time-resolved photoluminescence measurements on the isoelectronic series of oxygendeficient centers in amorphous silica related to silicon, germanium and tin atoms, which are responsible offluorescence activities at ∼4 eV under excitation at ∼5 eV. The dependence of the first moment of theiremission band on time and that of the radiative decay lifetime on emission energy are analyzed within atheoretical model able to describe the effects introduced by disorder on the optical properties of the defects.We obtain separate estimates of the homogeneous and inhomogeneous contributions to the measured emissionline width, and we derive homogeneous spectroscopic features of the investigated point defects (Huang-Rhysfactor, homogeneous width, oscillator strength, vibrational frequency). The results point to a picture in whichan oxygen deficient center localized on a heavier atom features a higher degree of inhomogeneity due tostronger local distortion of the surrounding matrix. For Si, Ge, and Sn related defects, the parameter λ, ableto quantify inhomogeneity, is 65, 78, and 90%, respectively.