Abstract
AbstractProcesses involved in the excited‐state relaxation of non‐bridging oxygen hole centers (NBOHCs) were studied in glassy SiO2 using luminescence, optical absorption and photoelectron emission spectroscopy. It was shown that photoexcited NBOHCs generally have three channels of relaxation. Along with radiative transitions responsible for the luminescence band at 1.9 eV, two non‐radiative channels caused by transitions between levels of photoexcited state were observed. The first non‐radiative channel was connected with transformation of the electron excitation energy to thermal lattice vibrations and represented an intracenter process of NBOHC luminescence quenching (the activation barrier was 0.05 eV). The second non‐radiative relaxation channel for excited NBOHCs was identified as thermally activated external luminescence quenching with the energy barrier of 0.46 eV. As a result of realization of the specified process, the transfer of the excitation energy from NBOHCs to oxygen‐deficient centers (ODCs) acting as electron emitters took place. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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