It is difficult to measure the in-plane directional electrical properties of a crystal sample without physical contact. This paper describes the measurement of in-plane unidirectional resistivity through electromechanical coupling. The degree of coupling was determined from acoustic velocity data measured using the Brillouin scattering method. The resistivity distribution in a ZnO crystal with a resistivity of less than 1 Ω m, (common in intrinsic wide band-gap semiconductors) was clearly detected through acoustic velocity at gigahertz frequencies. The resistivity values obtained from the acoustic wave velocities showed a good correlation with standard contact electrode measurements in the resistivity range of 0.03-1 Ω m. This noncontact measurement technique should be useful for measuring the microscopic distribution of in-plane resistivity in wide band-gap semiconductors, and is a powerful tool for experiments under extreme conditions, such as high pressure and/or high temperature.
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