Features of surface acoustic wave propagation in lithium niobate damaged by an electron beam

The propagation of surface acoustic waves (SAWs) in a thin-film aluminum waveguide of Δv/v type fabricated on a 128° Y-X LiNbO3 plate by lift-off lithography and direct writing by a 20-keV electron beamis studied experimentally. The temperature dependence of the phase of the signal passed through an SAW delayline exhibits steps and hysteresis. The line consists of such a waveguide and two interdigital transducers with acenter frequency of 486 MHz and is exposed to a nitrogen flow. The vapors of water-containing analytes introduced into the nitrogen flow cause anomalous phase changes. These changes are of opposite sign and more thanone order of magnitude greater than the phase changes observed under similar conditions in specimens fabricated by optical lithography. It is concluded that these phenomena offer possibilities for designing SAW humidity sensors with a low threshold of sensitivity.