Ozel Taner, Abdula Daner, Hwang Eric, Shim Moonsub
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
ACS Nano. 2009 Aug 25;3(8):2217-24. doi: 10.1021/nn900539t.
Interactions with the substrate that allow near perfect horizontal alignment in combination with large difference in the coefficient of thermal expansion are shown to lead to uniaxial compressive strain in as-grown single-walled carbon nanotubes on single crystal quartz. Temperature dependence of Raman G-band spectra along the length of individual nanotubes reveals that the compressive strain is nonuniform and can be larger than 1% locally at room temperature. A response of 27 cm(-1) upshift per % compressive strain is estimated for the G-band longitudinal optical phonon mode of semiconducting nanotubes. Comparison of Raman and atomic force microscope images suggests that the nonuniformity of the compression arises from the surface roughness induced by polishing. Effects of device fabrication steps on the nonuniform strain are also examined and implications on electrical performance are discussed.
与衬底的相互作用能实现近乎完美的水平排列，同时热膨胀系数差异巨大，这会导致在单晶石英上生长的单壁碳纳米管产生单轴压缩应变。沿单个纳米管长度方向的拉曼G带光谱的温度依赖性表明，压缩应变是不均匀的，在室温下局部可大于1%。对于半导体纳米管的G带纵向光学声子模式，估计每%压缩应变会有27 cm⁻¹的上移响应。拉曼图像与原子力显微镜图像的比较表明，压缩的不均匀性源于抛光引起的表面粗糙度。还研究了器件制造步骤对非均匀应变的影响，并讨论了其对电学性能的影响。
