Vibrational and mechanical properties of Si/Ge nanowires as resonators: A molecular dynamics study

In this work, we examine the vibrational and mechanical properties of clamped-clamped rectangular SixGe1-x and Si/SixGe1-x nanowires (NWs) using molecular dynamics simulations. A virtual atomic force microscope nanotip is used to drive the vibration. The frequency response, the beat vibration phenomenon and the calculation of mechanical properties such as quality factor Q and Young's modulus E are thoroughly analyzed. The influence of added mass and hydrogen passivation on the NW resonator performance is also demonstrated. The decreasing frequency trend with increasing Ge concentration was different for binary alloys and alloy superlattices, while it remained unaffected by the superlattice period. The beat vibration phenomenon driven by a single excitation was observed at elevated temperatures for all studied configurations. The resonance frequency decreases linearly with increasing temperature whereas the Q-factor follows a power law decrease. The Young's modulus E obtained through stress-strain computational experiments is found to be overestimated compared to the classical beam theory. Frequency decreases linearly as more atoms are added to the resonator. For low temperatures, the quality factor of composite Si/Ge resonators increased from 10(4) to 10(5) at T=23K, after performing hydrogen passivation on the NW free surfaces. The frequency shift due to the change in stoichiometry in a Si NW, alongside with representative snapshots of the vibrational behavior.