Thin-film microwave acoustic transducers of piezoelectric aluminum nitride (AlN) have been vacuum deposited by two methods. Aluminum nitride was deposited on metallic film substrates at 300°–1200°C by evaporating aluminum in the presence of either nitrogen gas dissociated in an ac discharge or in the presence of ammonia gas. Longitudinal ultrasonic waves were generated in a sapphire rod with a one-way-tuned conversion loss of 10 dB at 1700 MHz.
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Wauk et al. (1968) studied this question.
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