Single-crystal films of ZnO have been epitaxially grown on the (0001) and (011̄2) planes of sapphire by rf sputtering. Crystalline structures and electrical properties of the films were investigated. Surface acoustic wave (SAW) properties, including a phase velocity, a coupling coefficient, a propagation loss, and a temperature coefficient of delay, were measured for SAW propagating along the c-axis of the ZnO films, on the (011̄2) planes of sapphire. Availability of this structure for high-frequency SAW devices has been demonstrated by a filter with a 1050-MHz center frequency.

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SAW resonators have been fabricated from reflection strip arrays of ZnO films on borosilicate glass substrates by rf sputtering and standard photolithographic processing. Unloaded Q values were nearly 1000 and a linear temperature coefficient of about −10 ppm/°C was obtained when operated at a frequency of 100 MHz. Achievable Q values for ZnO/glass SAW resonators at this frequency are discussed.

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