Utilizing Mechanical Strain to Mitigate the Intrinsic Loss Mechanisms in Oscillating Metal Nanowires

Abstract

We utilize classical molecular dynamics to study energy dissipation (the Q factors) of doubly clamped copper nanowire nanoresonators undergoing flexural oscillations. We find that the application of tensile strain effectively mitigates both the intrinsic surface and thermal losses, with improvements in Q by a factor of 3-10 across a range of operating temperatures. We also find that the nanowire Q factors are not dependent on the surface area to volume ratio, but instead their aspect ratio, and that the Q factors exhibit a 1=T 0:70 dependence on the temperature T that is independent of strain. DOI: 10.1103/PhysRevLett.101.215502 PACS numbers: 62.20.Àx, 62.23.Hj, 62.25.Fg, 62.25.Jk Over the past decade, driven by their remarkable physical properties, nanowires have drawn considerable interest from the scientific community. These novel physical properties have motivated the development of novel nanowirebased nanoelectromechanical systems (NEMS), which have been proposed for chemical and biological sensing [1], force and pressure sensors [2], high-frequency resonators for next-generation wireless devices [3], and many other applications [4].Operationally, these nanowire-based NEMS utilize the nanowire as a resonating beam, where the nanowire oscillates continuously at or near its resonant frequency and where the desired change in local environment, i.e., force, pressure, or mass, can be detected by changes in the resonant frequency of the nanowire. Therefore, the key performance measure for nanowires is their quality (Q) factor, which measures the energy dissipated per vibrational cycle. A higher Q factor is critical to NEMS device performance and reliability as it implies less energy dissipation per vibrational cycle, which enables the nanowire to extend its operational lifetime by performing near optimal capacity for a longer period of time. Furthermore, for these sensing applications, the sensing resolution is inversely proportion to the Q factor; the mass sensitivity m [4] is defined aswhere DR is the dynamic range and M eff is the effective mass of the nanowire. From (1), it is evident that low Q factors are the key limiting factor to the development of ultrasmall, highly sensitive, and reliable NEMS. Nanowires can dissipate energy and thereby lower their Q factors through both intrinsic and extrinsic means; extrinsic losses occur due to interactions with the surrounding environment, typically through support or clamping losses and through gas or air damping [5], while intrinsic losses arise due to processes occurring within the nanowire itself, for example, due to surface-driven losses [6,7] and thermoelastic damping [5,8,9]. Various researchers have shown [6,7] that the surface loss increases in essentially a linear fashion with increasing surface area to volume ratio or decreasing nanowire size. Despite the experimental evidence demonstrating the importance of surface and thermal losses in degrading the nanowire Q factors, it is still not understood how these losses can be mitigated. One approach that h...

Intrinsic dissipation in a nano-mechanical resonator

“…Different variants of method A have been used earlier [35][36][37] in the computation of Q factor. In this method, we perturb the desired mode of the structure.…”

“…It has been shown that tensile stress can be used to enhance the Q factor for a nano-wire. 36,45 It would, therefore, be useful to study the role of tension for the case of intrinsic damping. We develop scaling relations for the variation of Q factor with the initial tension using continuum theory.…”

A review on nanomechanical resonators and their applications in sensors and molecular transportation

“…Different methods have been used in the literature to calculate the Q-factor. 138,144,[149][150][151] The maximum potential energy (E) is reduced to E À DE at the end of each oscillation cycle due to energy loss or damping, where DE represents the energy loss in each oscillation cycle. The Q-factor is thus defined as Q ¼ 2pE=DE.…”

Resonance of graphene nanoribbons doped with nitrogen and boron: a molecular dynamics study

“…Thus, the change of the external energy over time will be tracked for the calculation of Q . The external energy is defined as the difference of the potential energy before and after the initial excitation is applied to the testing sample [32]. Regarding the resonance frequency, a discrete Fourier transform will be applied [33].…”