Intrinsic and Extrinsic Losses in Nanoelectromechanical Systems

职务名称：内在和外在的损失在Nanoelectromagnetic systemsProject Goals：为了发展一个基本的理解，在纳米结构的能量损失，并利用这方面的知识，提高性能的nanostructuresNontechnical摘要：Nanoelectromagnetic系统（NEMS）已经吸引了显着的兴趣，因为他们承诺高频率和品质因数（Q）。然而，最近的许多实验研究已经观察到，NEMS的机械品质因数Q（定义为每单位周期存储的能量与损失的能量的比率）远低于理论预测。这种差异可以归因于纳米尺度上出现的新物理学，而经典理论中没有考虑到这一点。NEMS中可达到的频率与声子频率相当，这可以引入新的固有耗散源，例如Akhiezer阻尼，其可以显著降低品质因数。此外，由于纳米尺度下的表面与体积比更高，因此表面充当降低Q的额外耗散源。为了实现NEMS的全部潜力，重要的是要在纳米尺度上对所有耗散机制进行全面的物理理解。通过这些知识，可以设计高Q纳米结构。由于经典理论不能充分描述纳米尺度下的耗散，本项目的重点是发展原子和多尺度方法来理解纳米结构中的耗散。本项目将提供跨学科的研究，教育和培训研究生和本科生，研究成果将广泛传播，产生更广泛的影响。技术摘要：两种类型的机械损耗，即内在和外在的，将被考虑和理解。固有损耗或能量耗散机制是纳米结构固有的那些。固有损耗的流行来源是Akhiezer阻尼、热弹性阻尼、表面、缺陷等。大多数纳米结构在流体介质中工作，因此除了固有损耗之外，还需要考虑定义为由流体引起的损耗的非固有损耗。 该项目的主要目标是（i）开发原子和多尺度计算方法，以了解各种一维和二维纳米结构中的固有损耗。综合理论模型Akhiezer，热弹性，缺陷，表面和其他来源的内在耗散将开发。(ii)发展原子和多尺度计算方法来理解外在损失。为了确定外在损失，耦合流体和结构分析是必要的。为了计算作用在纳米结构上的流体力，将开发一种全面的多尺度方法。流体分析的多尺度方法将与纳米结构分析的多尺度方法相结合，以确定外在损失。 (iii)通过将计算的品质因数与实验数据进行比较，确定计算方法的有效性。此外，NEMS的各种应用，如高频谐振器，能量收集和质量传感将被追求。

Title: Intrinsic and Extrinsic Losses in Nanoelectromechanical SystemsProject Goals:To develop a fundamental understanding of energy losses in nanostructures and to exploit this knowledge for enhanced performance of nanostructuresNontechnical Abstract:Nanoelectromechanical systems (NEMS) have attracted significant interest as they promise high frequencies and quality factors (Q). However, many recent experimental studies have observed that the mechanical quality factor, Q, defined as the ratio of the energy stored to the energy lost per unit period, of NEMS is much lower than those from theoretical predictions. This discrepancy can be attributed to the novel physics that arises at the nanoscale and is not accounted for in the classical theory. The attainable frequencies in NEMS are comparable to the phonon frequencies and this can introduce new sources of intrinsic dissipation, such as Akhiezer damping, which can significantly reduce the quality factors. In addition, as the surface to volume ratio is higher at nanoscale, surfaces act as an additional source of dissipation reducing the Q. To realize the full potential of NEMS, it is important to develop a comprehensive physical understanding of all dissipation mechanisms at nanoscale. Through this knowledge, high Q nanostructures can be engineered. Since classical theories do not adequately describe dissipation at nanoscale, the focus of this project is to develop atomistic and multiscale approaches to understand dissipation in nanostructures.This project will provide interdisciplinary research, education and training of graduate and undergraduate students and the research results will be widely disseminated for broader impact.Technical Abstract:Two types of mechanical losses, namely intrinsic and extrinsic, will be considered and understood. Intrinsic losses or energy dissipation mechanisms are those that are inherent to the nanostructure. Popular sources of intrinsic dissipation are Akhiezer damping, thermo-elastic damping, surfaces, defects, etc. Most nanostructures operate in a fluid medium, so in addition to intrinsic losses, extrinsic losses, defined as the dissipation caused by the fluid, also needs to be taken into account. The key objectives of this project are to (i) Develop atomistic and multiscale computational approaches to understand intrinsic losses in a variety of one-dimensional and two-dimensional nanostructures. Comprehensive theories to model Akhiezer, thermo-elastic, defects, surfaces and other sources of intrinsic dissipation will be developed. (ii) Develop atomistic and multiscale computational approaches to understand extrinsic losses. To determine extrinsic losses, coupled fluidic and structural analysis is necessary. To compute fluidic forces acting on the nanostructure, a comprehensive multiscale approach will be developed. The multiscale approach for fluidic analysis will be coupled with a multiscale approach for nanostructural analysis to determine extrinsic losses. (iii) Establish validation of the computational approaches by comparing computed quality factors with experimental data. In addition, various applications of NEMS such as high frequency resonators, energy harvesting and mass sensing will be pursued.