• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2166-2172
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• 2007

In this study a low-signal equivalent circuit based on the Double Schottky Barrier model is proposed for ZnO-based varistor. Since pin-lead inductance and stray capacitance are considered in pin-lead type ZnO varistor these inductance and capacitance could be removed from the experimental dielectric data of the varistor. According to the equivalent circuit simulation results the higher the varistor-voltage of varistor sample the capacitance of dielectric layer is larger, and the capacitances of semiconducting layer and depletion layer are smaller, while the parallel resistances of semiconducting layer and depletion layer are more larger values. Spectra of the dielectric loss factor $tan{\delta}$ show 2 peaks in low frequency and high frequency regions respectively. The low-frequency peak is due to the relaxation by deep donors and the high-frequency peak is due to the relaxation by shallow donors. Above results are well consistent with the theoretical mechanism of ZnO varistor.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.921-924
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• 2003

A current-voltage relation for Positive Temperature Coefficient of Resistance (PTCR) ceramic was derived and compared with the experimental data. The new current-voltage relation was developed based on Heywangs double Schottky barrier model and a bias distribution across the grain boundary. The voltage limitation V < 4${\Phi}$$\sub$b/ suggested by Heywang is no longer necessary in the new expression for the voltage dependence of the resistance. The pulsed voltages were applied to the PTCR ceramic specimen in order to avoid possible temperature variation during the measurement.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.231-235
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• 2019

We investigated the facile and effective strategy for sensitive and selective $C_2H_5OH$ sensors based on the In-decorated NiO nanoigloos. The In-decorated NiO nanoigloos is fabricated by RF sputtering using 750 nm-diameter polystyrene beads using a soft-template. The morphological evolution based on the Van der Drift model was generated through a heterojunction between In metal and NiO, resulting in a pyramidal rough surface. Upon decorating the In on the NiO surface, high sensitivity and selectivity to $C_2H_5OH$ were observed, and gas sensing mechanism was demonstrated by a high surface-to-volume and double Schottky barrier. We are confident that the method presented in this study will have a significant impact on the fabrication of effective nanostructures and their application for the gas sensors.