Mechanical Loss Mechanisms in c-axis Gallium Nitride Nanowires

c 轴氮化镓纳米线的机械损耗机制

• 批准号: 0856261
• 负责人: Charles Rogers
• 金额: $ 35万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0856261&HistoricalAwards=false
• 关键词: Mechanical; Loss; Mechanisms; axis; Gallium

The key goal of the proposed research is to experimentally measure quality (Q)-factors for c-axis oriented Gallium Nitride (GaN) nanowires (NWs) over a large ensemble of NW dimensions, while simultaneously developing novel multiscale, coupled physics computational models to quantify the dominant loss mechanisms. A particular emphasis will be placed on understanding size and surface effects on the relative importance of the individual loss mechanisms across a technologically relevant range of length scales. Experimentally, this will be achieved by providing, for the first time, a comprehensive body of experimental data on mechanical resonance position and resonance linewidth for a large ensemble of c-axis GaN NWs, and over a wide range of NW lengths (1 to 20 microns), diameters (10 to 100 nm), vibrational frequencies (100 kHz to 100 MHz), and temperature (4 K to 400 K). Novel multiscale modeling approaches, including the surface Cauchy-Born model and coupled nanoscale energy and momentum equations that capture, for the first time, surface stress effects on both the thermal and mechanical fields, will be developed to simulate and quantitatively predict Q-factor degradation due to intrinsic surface losses and thermoelastic damping of NWs.If successful, this research will make original contributions in the understanding of how surfaces are implicated in the mechanical losses of GaN NWs. It will additionally elucidate the fundamental mechanisms governing size, and temperature effects on energy dissipation in GaN NWs, while delineating the length scales at which each loss mechanism dominates. This project will further quantify, for the first time, the errors introduced in NW modeling if standard bulk continuum models that neglect surface effects are scaled down to the nanoscale. The project further focuses on the involvement of under-represented minorities in the nanoengineering research and education process. It will leverage the training of future nanoengineers in both nanoscale modeling and experiment by the integration of the proposed research into the curriculum. Results and insights will be broadly distributed through professional and physics educational websites.

拟议研究的主要目标是通过实验测量c轴取向氮化镓（GaN）纳米线（NW）在NW尺寸的大集合上的质量（Q）因子，同时开发新的多尺度耦合物理计算模型来量化主要的损耗机制。 将特别强调了解尺寸和表面效应对各个损失机制在技术上相关的长度尺度范围内的相对重要性的影响。 在实验上，这将通过第一次提供关于c轴GaN纳米线的大集合体和宽范围的纳米线长度的机械谐振位置和谐振线宽的实验数据的综合体来实现（1至20微米）、直径（10至100 nm）、振动频率（100 kHz至100 MHz）和温度（4 K至400 K）。新的多尺度建模方法，包括表面柯西-玻恩模型和耦合的纳米级能量和动量方程，第一次捕捉到表面应力对热和机械场的影响，将被开发用于模拟和定量预测由于纳米线的固有表面损耗和热弹性阻尼引起的Q因子退化。如果成功，这项研究将在理解表面如何与GaN纳米线的机械损耗有关方面做出原创性贡献。 它还将阐明控制GaN纳米线中能量耗散的尺寸和温度效应的基本机制，同时描绘每个损耗机制占主导地位的长度尺度。 该项目将进一步量化，第一次，在NW建模中引入的错误，如果忽略表面效应的标准散装连续模型按比例缩小到纳米级。该项目进一步侧重于代表性不足的少数民族参与纳米工程研究和教育进程。它将通过将拟议的研究整合到课程中，来利用未来纳米工程师在纳米级建模和实验方面的培训。结果和见解将通过专业和物理教育网站广泛传播。