波長可変ピコ秒超音波法の開発と酸化物薄膜の減衰評価法の提案

概要

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Thin-film mechanical resonators are promising for high frequency bandpass filters. Amorphous oxide thin films are expected to be important candidates because they are free from grain scattering loss. However, it has been difficult to characterize their acoustic properties, especially attenuation, which is a key parameter for designing a high-Q resonator. Here, we present a novel methodology for evaluating ultrasonic attenuation in amorphous oxide thin films deposited on silicon substrate very high frequencies between 200 and 300GHz. This method uses the high sensitivity of the refractive index of light in silicon to the wavelength near 400nm. Detecting Brillouin oscillations from silicon substrate, which is caused by the transmitted acoustic wave, we can evaluate the frequency dependence of the attenuation coefficient in the thin film through an inverse calculation.
2010-11-25