Diamond-SAW devices: a reverse fabrication method

Abstract

Surface acoustic wave (SAW) devices are key components in modern wireless communication systems. Besides being used as reflective delay lines, filters or resonators, SAW devices can be used as sensors and fixed-code identification tags. Due to their high-acoustic velocity, diamond films can be combined with piezoelectric materials to fabricate diamond-based SAW devices with potential for high frequency applications. This paper presents results of coating commercial SAW delay lines with diamond films. The films were deposited on lithium niobate under different conditions in a hot filament chemical vapour deposition system. Seeding was performed using 6-12 mu m diamond grit and 20-30 nm nano-diamond particles based suspensions. After tuning the deposition conditions, dies of 74 MHz delay lines were coated with diamond. The quality, morphology and conformability of the coatings were evaluated by scanning electron microscopy (SEM) and Raman spectroscopy. The integrity of the interdigitated transducers (IDTs) after deposition was evaluated by SEM. S-parameters of as-bought and diamond-coated dies were measured using a network analyser. Although the frequency response is attenuated after diamond deposition, integrity of the IDTs and the operating principle of the devices are kept intact. These preliminary results open the door to a simplified fabrication procedure of diamond-based SAW devices.