Self-focused high frequency ultrasonic transducers based on ZnO piezoelectric films

A micromachined self-focusing high frequency ultrasonic transducer was fabricated with a 13μm thick ZnO film deposited on a silicon substrate by sputtering. X-ray diffraction shows that the film has a high (002) orientation. The element aperture size of the transducer was 2.5mm, and the fundamental resonant frequency was designed to be over 200MHz with approximately 28% bandwidth through only one matching layer. Experimental results show that this type of focused high frequency ultrasound device may have potential for cellular microstructure imaging and skin cancer detection.