Acoustic properties of sputtered glass at microwave frequencies

The published literature contains little information on the acoustic properties of thin dielectric films produced by sputter deposition. The longitudinal velocity and impedance of a sputter-deposited glass film, one-quarter wavelength thick, has been measured in the vicinity of 400 MHz. Such a layer produces a near-optimum acoustic power transfer between sapphire and water. Curve fitting the predicted return loss against frequency to the experimental impedance transformer response provides a convenient method for the determination of the layer’s acoustic properties.