Abstract
We present an evaluation of attenuation of elastic waves in the GHz range, based on the decay of thickness-stretch resonances of plates. We measured the elastic response of micro-scale aluminum plates, using a laser-ultrasound technique. The thermo-elastic laser excitation provides significant coupling into thickness-stretch modes in the frequency range above 1.5 GHz. To suppress interference from other resonant and transient modes, we used an excitation spot size well above the plate thickness and applied signal processing in the time and frequency domain. We adapted existing theory on the decay of thickness-shear modes to apply for thickness-stretch modes, validated the derived theory with simulations, and applied it to experiments. A set of samples with different thicknesses in the range of 1.1–2.15 μm allowed us to obtain damping values in the corresponding frequency range of 1.5–3 GHz.
Highlights
We present an evaluation of attenuation of elastic waves in the GHz range, based on the decay of thickness-stretch resonances of plates
Our investigation is focused on aLðf Þ, the attenuation of longitudinal waves, which are predominant in bulk acoustic wave filters
We present our results as a quality factor Qðf Þ 1⁄4 f =2aL
Summary
ABSTRACT We present an evaluation of attenuation of elastic waves in the GHz range, based on the decay of thickness-stretch resonances of plates. The thermo-elastic laser excitation provides significant coupling into thickness-stretch modes in the frequency range above 1.5 GHz. To suppress interference from other resonant and transient modes, we used an excitation spot size well above the plate thickness and applied signal processing in the time and frequency domain.
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