Electron trapping center and SnO2-doping mechanism of indium tin oxide

Indium tin oxide (ITO) and Er3+-doped ITO powders were prepared by a conven tional ceramic method. The density of ITO powders and optical absorption sp ectra of Er3+ ions in Er3+-doped ITO were measured as a function of the SnO 2 doping level, The results obtained were discussed in terms of the trappin g center for immobile electrons in ITO. Observed densities of ITO powders w ere in good agreement with those calculated from their lattice parameters, assuming that the immobile electrons were trapped at the excess interstitia l oxygen. The optical absorption spectra of Er3+-dopcd ITO indicated that s ome In3+ ions in ITO were surrounded by 7 and/or 8 oxygen ions; the increas e in the coordination number of In3+ from 6 in In2O3 to 7 and/or 8 in ITO m ust be caused by the introduction of excess interstitial oxygen into the qu asi-anion site in the C-type rare-earth lattice upon SnO2 duping. II was co ncluded that the immobile electrons in ITO air trapped at the excess inters titial oxygen, and that the mechanism of conduction carrier generation and compensation upon SnO2 doping into In2O3 can be expressed by the defect equ ation, 2SnO(2) ---> 2Sn(Ln)(.) + 2(1 - z)e' + zO(l)" + 30(o)(x) + (1 - z)/2 O(2).