Surface acoustic wave band gaps in micro-machined air/silicon phononic structures — theoretical calculation and experiment

Abstract

Abstract In this paper, we investigate the band gaps of micro-machined air/silicon phononic structures both theoretically and experimentally. Based on the plane wave expansion method, dispersion relations of the surface and bulk modes with square lattices in air/silicon two-dimensional phononic structures are calculated and discussed. Band gap widths due to the filling fraction and temperature variation are also analyzed. On the experimental side, generation and reception of high frequency surface acoustic wave in this band structure are realized by a pair of interdigital transducers (IDT) with frequency around 200 MHz. Details of the fabricating process of the phononic structure and the high frequency surface wave generating and receiving IDTs are given. The results demonstrate clearly the existence of SAW band gap in the micro-machined phononic structure and this study may serve as a basis for studying the band gap of SAW in micro-machined phononic structure with the dimension in the order of micrometer and find applications in the RF SAW devices.