Light emission from tin-dioxide crystals

The luminescence spectra of SnO$_2$ crystals are studied in the temperature range from 5 to 40 K. Broad luminescence bands in the visible spectral region are attributed to transitions from the donor levels of oxygen vacancies and interstitial tin atoms to the acceptor levels of another type of intrinsic defects that are apparently formed from tin vacancies and interstitial oxygen atoms. It is found that emission related to one of the exciton-defect complexes with the minimum binding energy is enhanced, as the crystal is heated from 5 to 30 K. The distinguishing feature of this complex is its anomalously weak coupling with crystal-lattice vibrations.