Surface acoustic wave hydrogen sensor with a multilayer structure: preliminary results

Preliminary results concerning a hydrogen sensor based on a multilayer structure in a Surface Acoustic Wave dual-delay line system are presented. The sensor material consists of two layers performed in two different vapor deposition processes. The first one is a 720 nm CuPc layer, the other one -- a 20 nm thin palladium film. This structure was formed in a one of the dual-delay line system on a LiNbO3 Y-cut Z-propagation substrate. In such a multilayer structure can detect hydrogen in a medium concentration range (from 0.25% to 3% in nitrogen), even at room temperature. The sensor has a very good sensitivity, stability and is entirely reversible. The response and recovery times are very short (approximately 200 s - 800 s), which is very important from the practical point of view.