Mott–Schottky behavior of strongly pinned double Schottky barriers and characterization of ceramic varistors

Abstract

Nature of the Schottky-type barrier of highly dense SnO 2 systems displaying nonohmic behaviorThis work studies the capacitive behavior of an intergranular double Schottky barrier, which describes nonlinear charge transport in polycrystalline semiconductors. It is found that: ͑i͒ a widely applied version of the Mott-Schottky equation can be inadequate, and can lead to significant errors; ͑ii͒ a property called strong barrier pinning ͑SBP͒, underlies most attempts to obtain physical parameters from C -V measurements; and ͑iii͒ under SBP, known results from one-sided Schottky barriers can be used to analyze C -V response, showing that correct physical parameters are obtained at low frequency and that high frequency measurements are not advantageous. A new characterization method is introduced, which allows high voltage devices to be directly measured, and yields comparative information about average donor density and barrier height. Besides its technological applicability, the method simplifies the study of scale effects. Experimental results support the theoretical considerations and the proposed characterization method. The usefulness of the method is illustrated by studying the effects of current-pulse degradation on the physical parameters of high voltage varistors.

Niobium–Zirconium Oxynitride Nanotube Arrays for Photoelectrochemical Water Splitting

“…By way of illustration, the flat-band potential values were inferred from the high-frequency MS plots to exclude the capacitance's contribution from the Helmholtz layer and the surface states. 66 Note that the plot for the ammonia-annealed sample is not completely linear, which indicates the presence of lattice defects. 67 Note that the bandedge positions of the annealed samples can be feasibly determined by using the previous data side by side with the bandgap energy typically obtained from Tauc plots.…”

Bulk-grain resistivity and positive temperature coefficient of ZnO-based varistors

“…The geometrical capacitance C HF appears at about 10 8 -10 9 Hz, depending on the position of the highest-frequency loss peak. 14 Up to this point, the discussion is generally valid for any polycrystalline semiconductor. We now focus on ZnO-based varistors.…”

Low-resistance and high-resistance states in strontium titanate films formed by the sol–gel method

“…The change in the resistance of strontium titanate can be explained as follows. Upon applying a voltage to the metal/strontium titanate/metal structure, redistribu tion of defects (strontium and oxygen vacancies) near the grain boundaries affects the height of the intergrain potential barrier (the double Schottky barrier) [8,12,13]. Oxygen vacancies are charged positively [3,8,14,15].…”