100 MHz Band Ultrasonic Transducers Utilizing Epitaxially Grown ZnO Films

Abstract

A 100 MHz band ultrasonic transducer with a short pulse response is realized using a 15 µm-thick high quality epitaxial ZnO film. The film is deposited by rf magnetron sputtering on a gold electrode film grown epitaxially on the c-plane of a sapphire. It was found that well oriented thick (>10 µm) ZnO films with little polycrystalline nuclei can be grown only on highly (111)-oriented gold films whose σ for the Au(111) rocking curve was less than 0.5°. Some examples of high resolution (∼10 µm) imaging are demonstrated with the 100 MHz band transducer.