J0406-1-6 サブテラヘルツ超音波によるナノ薄膜の弾性定数計測(超音波計測・解析法の新展開(1))(超音波計測・解析法の新展開(1))

概要

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Elastic stiffness of ultrathin films is studied by the pump-probe technique using the femtosecond light pulse. This method generates the longitudinal sub-terahertz ultrasonics by the irradiation of the specimen with the femtosecond light pulse, and they are preferentially detected by the probing pulse. When the film thickness is relatively small, longitudinal standing waves are generated in the thickness direction. For the thicker films, the sub-terahertz longitudinal-wave pulses are generated near the film surface, propagate in the thickness direction, and reflect at the interface between the film and substrate. By measuring the resonance frequencies and round-trip time, the elastic stiffness is determined. In this study, it is found that the elastic stiffness of polycrystalline Pt films on MgO substrates shows the relationship with the residual strain. The change ratio is significantly large and it is confirmed that the conventional acoustoelasticity cannot explain it quantitatively.
2009-09-12