Department of Materials Science and Engineering, The Pennsylvania State University, State College, PA 16802, USA.
Nanotechnology. 2017 Feb 10;28(6):065703. doi: 10.1088/1361-6528/28/6/065703. Epub 2017 Jan 3.
Previous reports suggest that Raman peaks in uniaxially loaded nanowires with diamond cubic and zinc blende crystal structures shift at rates that are significantly different from bulk specimens. We have investigated the first order Raman scattering from individual, free-standing, [111] oriented GaP nanowires ranging from 75 to 180 nm in diameter at uniaxial tensile stresses up to 5 GPa. All of the phonon modes were shifted to frequencies lower than previously reported for bulk GaP, and significant splitting of the degenerate transverse optical mode was observed. A general analysis method using single and double Lorentzian fits of the Raman peaks is presented and used to report more accurate values of the phonon deformation potentials (PDPs) that relate uniaxial strains to Raman peak shifts in GaP. A new set of PDPs determined from the nanowires revealed that the they have elastic moduli and failure strains that are consistent with bulk GaP. The analysis method eliminated the anomalous, inconsistent deformation behavior commonly reported in Raman-based strain measurements of nanowires, and can be extended to other materials systems with degenerate phonons.
先前的报告表明，具有金刚石立方和闪锌矿晶体结构的单轴加载纳米线的 Raman 峰的移动速率与体样本显著不同。我们研究了从直径为 75 到 180nm 的单个、独立、[111]取向 GaP 纳米线在高达 5GPa 的单轴拉伸应力下的一阶 Raman 散射。所有声子模式的频率都移到了比以前报道的体 GaP 更低的位置，并且观察到简并的横向光学模式的显著劈裂。提出了一种使用 Raman 峰的单和双洛伦兹拟合的通用分析方法，并用于报告与 GaP 中 Raman 峰移动相关的声子变形势 (PDP) 的更准确值。从纳米线确定的一组新的 PDP 表明，它们具有与体 GaP 一致的弹性模量和失效应变。该分析方法消除了 Raman 基纳米线应变测量中通常报道的异常、不一致的变形行为，并且可以扩展到具有简并声子的其他材料系统。
