ISOTHERMAL CAPACITANCE TRANSIENT SPECTROSCOPY STUDY ON TRAP LEVELS IN POLYCRYSTALLINE SNO2 CERAMICS

The unusual sigmoidal behavior between electrical resistivity and inverse temperature in polycrystalline porous SnO2 was intensively investigated by detecting the localized traps formed at the interparticle through the measurement of Isothermal Capacitance Transient Spectroscopy. A trap of 1.0 eV was evaluated at a higher temperature range of 460-500-degrees-C, and 0.6 eV trap at a lower temperature range 200-280-degrees-C. It seems that the trap of 1.0 eV originates from O2- and 0.6 eV from O- defect center. Time constants which were determined at the peak position of ICTS spectra, S(t), were increased with the increase of temperature at the intermediate temperature range, indicative of the competition among various kinds of traps. The active competition among various traps is one of the causes that result in prominent gas sensitivity in polycrystalline porous SnO2.