Electrical conduction in pure stoichiometric nickel oxide
Abstract
Three and four-probe resistivity measurements were conducted on high purity arc-transfer grown single crystals of NiO which had been annealed to be nearly stoichiometric. These measurements revealed the existence of a surface layer with enhanced conduction in comparison to that of the bulk. Annealing increases the bulk resistivity by more than 10 orders of magnitude near room temperature. The measured bulk resistivity is larger than previously reported, attaining a value of greater than 10$\sp{16}\Omega$cm below 100$\sp\circ$C. The activation energy is 1.65 eV and no change in slope was observed at the Neel temperature. The bulk thermoelectric-power, measured with a specially designed four-probe experiment, yielded a weakly temperature dependent value of +0.9 mV/K at temperatures above the Neel point. Several observations of anomalous behavior, including a thermoelectric response time much greater than the thermal response time of the sample remain unexplained. It is not possible to definitively determine the nature of the conduction process from these measurements, although, a small polaron model in the hopping regime, with the hole concentration fixed by trace impurities, best fits the data. An itinerant band model in the intrinsic regime cannot be ruled out.
Degree
Ph.D.
Advisors
Zandt, Purdue University.
Subject Area
Condensation|Electromagnetism
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