半導体微小機械共振器中のモード間結合効果の解明と超高感度テラヘルツ波検出への応用

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The objective of this study is to clarify the mode coupling effect in MEMS beam resonators and explore its possible application in high sensitivity terahertz sensing. In the research of this year, we continued investigating the physical origin of the mode coupling effect by measuring the thermally modulated mode coupling strength.The mode coupling strength is determined by the resonance frequency shift when the coupled high frequency mode is excited simultaneously with the lower mode. As an input heat is applied to the MEMS beam, the MEMS beam is heated up to the buckling condition, which changes the mode coupling strength, as well as the mechanical nonlinearity of the MEMS beam. We have found that the mode coupling strength change has a very similar trend with the mechanical nonlinearity, indicating that these two effects may have the same origin. In addition, we have demonstrated that the mechanical nonlinearity mainly comes from the extended beam length during the mechanical oscillation, and can be controlled by the internal strain in the beam. This has been verified by inputting heat or introducing lattice mismatch in the MEMS beam. These results are very useful for understanding the fundamental physics in MEMS beam resonators, and hence are useful for designing highly sensitive MEMS detectors.