K. Mukae et al., Electronic interface states at grain boundaries in ZnO : Pr varistors by single grain boundary measurements, J EUR CERAM, 21(10-11), 2001, pp. 1871-1874
Electronic interface states at grain boundaries in ZnO:Pr varistors were di
rectly observed by single grain boundary measurement. Photo-capacitance spe
ctroscopy and photo-isothermal capacitance transient spectroscopy(photo-ICT
S) were applied to these experiments. Photo-capacitance spectrum in the nea
r infrared region showed a peak at 1380 nm, i.e. 0.9 eV. Since this peak is
originated by electron excitation from the interface states at the grain b
oundary, the energy for this peak indicates that the electronic states at t
he grain boundaries are located at 0.9 eV below the top of the double Schot
tky barrier. This result is the direct evidence which shows the value of th
e energy level of the interface states in ZnO varistors. Moreover the ICTS
peak shifted to shorter range by the irradiation of 1380 nm light. The phot
o-intensity change of ICTS peaks revealed the linear relation between emiss
ion rate of the interface states and the light intensity. (C) 2001 Elsevier
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