X-ray photoelectron spectroscopy investigation of segregation processes at Sb and In doped SnO2

Sb and In doped SnO2 powders and single crystals were prepared. The kinetics and thermodynamics of segregation processes of doping elements in dependence on annealing temperature was investigated by X-ray photoelectron spectroscopy (XPS). For 24 h annealing time of SnO2 Single crystals the thermodynamic equilibrium is already reached for Sb above 850 degreesC and for In at 1000 degreesC. For doped SnO2 powders no equilibrium is observed under these conditions. The activation energy of diffusion of doping elements in tin oxide single crystals calculated from the experimental segregation kinetics data amounts to 90 kJ/mol for Sb and to 67 kJ/mol for In. The apparent activation energy in doped powders is much higher and depends on the doping concentration. The diffusion coefficients in the temperature range from 600 to 900 degreesC are at the single crystals in the range of 10(-19)-10(-16) cm(2)/s. (C) 2002 Elsevier Science B.V. All rights reserved.