|Alternative Title||Raman Spectroscopy and Electron Transport of Single-Walled Carbon Nanotubes
|Place of Conferral||兰州
其次，用电子束蒸发和快速热退火工艺在SWNT-FETs表面自组装了金纳米颗粒，制备出新奇的SWNT@金纳米颗粒。表面金属纳米颗粒的库仑作用改变了SWNTs的电子结构。当温度低于150 K时，在长约2 µm的导电沟道中观察到强烈的电流振荡。
最后，用低功函数的金属（Sc, Sm, Al等）作为源、漏电极材料制备了性能稳定的n型SWNT-FETs。所制备的SWNT-FETs的开关电流比大于3个数量级，并且在约5 µm的导电通道中呈现出近似弹道输运的性质，电导约为0.02 G0。|
|Other Abstract||This thesis presents the main findings in my PhD project on the Raman spectrum and the electron transport properties of single-walled carbon nanotubes (SWNTs). Resonance Raman spectroscopy is firstly used to characterize the structural properties of SWNTs under various external perturbations, including strain, nanoparticles decorated, electrostatic gating, electrical heating, et al. Afterwards, the electron transport mechanisms in two novel SWNTs hybrid structures, SWNT@Au-NCs (gold nanocrystals) and SWNT@Cn (carbon chains), are investigated. At last, stable n-type SWNT field effect transistors (FETs) are successfully fabricated. One conventional optical lithography compatible method is developed for sub-10 nm nanogap electrode arrays fabrication, which has been proven an excellent way for nano-sized devices integration.
Abnormal Raman scattering from a large diameter ultralong SWNT is studied in detail. Along the SWNT, the Raman spectra show the frequencies of 1553, 1563, and 2597 cm-1 for G+, G–, and G′ peaks, respectively, much lower than the corresponding frequencies well reported both experimentally and theoretically. The significant downshifts in the peaks frequencies can be attributed to self-built tensile strain which is likely caused by carbon nanodots decorated on the tube. After infrared laser heating is performed to one point of it, all the Raman modes are found to shift to higher frequencies and approach to their conventional values. We suggest that the SWNTs with larger diameters easily possess such self-built strain compared to small-diameter SWNTs because of the weaker curvature effect for the larger ones.
In situ Raman measurements have been carried out on a thin bundle of SWNTs in FET configuration at various gate voltages. Two excitation lasers with the photon energy of 1.96 eV and 2.41 eV are selected to excite the Raman scattering modes of metallic and semiconducting SWNTs in the bundle, respectively. For the metallic SWNTs, the G– Raman mode is found to shift to higher frequencies and narrow down its line shape at negative gate voltages, but be insensitive to positive gate voltages. These findings confirm that the Kohn anomaly exists in a thin SWNTs bundle and that the LO phonon mode changes along with the position of the Fermi level in the metallic SWNTs. In contrast, semiconducting SWNTs do not show any observable changes in the Raman spectra.
Electrical bias voltages tuned Raman spectroscopic of SWNT-FET show that the G pe...|
高平奇. 单壁碳纳米管拉曼光谱及电输运性质研究[D]. 兰州. 兰州大学,2010.
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