Acoustoelectric probe for d33 measurement on piezoelectric thin films

Abstract

An acoustoelectric probe capable of measuring the d33 constant of piezoelectric thin films is presented. The principle used is the direct piezoelectric effect: a mechanical stress is applied to the film surface and the subsequent voltage generated is measured and compared with a reference. The mechanical stress consists of a rf acoustic longitudinal wave generated by a piezoelectric plate in a metallic rod and through this applied to the film free surface. The probe is mounted in a classical electrical probe in order to easily position and perform reliable measurements. The instrument permits the exploration and mapping of the piezoelectric properties of the deposited thin film without any need for a top electrode deposition. This allows an easy mapping of the film properties in a nondestructive way. A sensitivity of 1 pC/N has been estimated. Measurement of piezoelectric properties under a dc bias field, as required for relaxor thin films, are also possible. The structure and the design of the probe, as well the complete experimental setup, are presented. Some results of measurements made on different materials are reported.