氮化鎵一維奈米線之合成與拉曼性質分析

奈米線、奈米尖錐、奈米帶等一維奈米結構因具有獨特的光性、電性和機械性質而成為現今的熱門研究領域。目前半導體的研究已經進入了奈米級的進展，在如此微小的世界裡，拉曼散射光譜是一項強而有力的分析工具，具有簡單、低成本、快速、以及非破壞性量測等優點。在未來奈米元件的製程與分析上，扮演著不可或缺的角色。本研究中，以化學氣相層積法將氮化鎵一維奈米線成長在矽晶片基板上，使用共焦拉曼微光譜儀來做一連串的拉曼量測與分析。透過掃描式電子顯微鏡可觀察出氮化鎵一維奈米線的直徑約在100奈米左右，而X光繞射儀與穿透式電子顯微鏡證明了氮化鎵奈米線屬於六角晶系、以[100]為成長方向，並具有高度結晶品質。單根氮化鎵奈米線的拉曼頻譜顯示出一般六角晶系的聲子特徵，並且E2(high)模態具有很窄的半高寬，代表很好的晶體品質。在單根氮化鎵奈米線的偏極化拉曼量測上，顯示出不尋常的偏極化響應，與一般文獻以及模擬上迥然不同。此差異經過推測，極有可能是由於單根氮化鎵奈米線對於不同偏振方向的雷射光有不同的吸收所造成，另外，透過偏極化的拉曼量測，並配合模擬結果，可得知空間中氮化鎵的晶軸方向。另外，在683 cm-1與714 cm-1這兩個頻率的地方有觀測到兩個微弱且寬的峰，但此兩處仍未被以發表的文獻所討論。由於本研究所使用的單根氮化鎵奈米線具有極大的比表面積，因此推測此處應為氮化鎵奈米線本身所產生的表面聲子模態，但仍需要更進一步的研究與分析。

關鍵字

氮化鎵；奈米線；拉曼；偏極化

並列摘要

Recently, GaN and related compounds semiconducting nanowires have attracted great attention as building blocks in electronics, optoelectronics and sensors. It has been reported that the optical properties of nanosized materials are strongly relevant to the crystalline quality, growth orientation, extended structural defects and surface defects. Among all characterization techniques, Raman scattering can be the best candidate because the above-mentioned information can be obtained in an easy as well as non-destructive way.In this work, GaN nanowires were grown on Si substrate via the chemical vapor deposition method with Ni as the catalyst in the vapor-liquid-solid mechanism. The resulting nanowires were found to be hexagonal wurtzite in structure and [100] in preferred growth orientation by using transmission electron microscopy. For single nanowires Raman measurement, GaN nanowires were further dispersed on Si substrate with pre-coated patterned Au film to prevent the background signal from Si.Raman scattering measurement was performed using confocal Raman microscope (HORIBA Jobin Yvon, LabRAM HR800) with 633 nm Laser. The polarization vector was rotated by a half-wave plate positioned at entrance of Laser.The GaN single nanowire shows conventional Raman characteristics of wurtzite structure, such as 529, 559, 567, 724 cm-1 for A1(TO), E1(TO), E2(high), A1(LO) phonon mode, respectively, and sharp line-width of E2(high) mode of 4 cm-1 indicating high crystalline quality. The polarized Raman spectra of GaN single nanowire exhibits unusual polarized response, which is out of expectation from a simple simulation based on a*-directed wire. The difference is assigned to the shape effect of the nano-size-wire, as understood by the distortion of linearly polarized scattering states of the electromagnetic field across the nanowire boundary. Additionally, the angle-dependent Raman spectra of individual nanowires reveal different polarized behaviors, as a result of various c-axis orientated directions. After combination with the simulation, the spatial orientation of GaN nanowire crystallographic axes, as well as crystal quality can be determined. Accordingly, this is a powerful analytical and in-situ technique in future application of nano-devices, such as single nanowire FET, single nanowire photonics, for probing structural and optical properties. Furthermore, two broadband centered at 683 cm-1 and neighbored beside A1(LO) mode are supposed to the surface mode of nanostructure due to a large surface-to-volume ratio. Also, there is a good agreement with the prediction of surface mode but still essentially unexplored.In short, this report demonstrates a convenient method to obtain the profile of single GaN NW. For those who may concern the orientation, facets, defects of the NW, this technique is indispensable especially for realizing NW-integrated system.

並列關鍵字

GaN ； nanowires ； Raman scattering ； polarization

參考文獻

[1.1] S. Nakamura, Stephen. Pearton and G. Fasol, “The Blue Laser Diode”, Springer, Berlin (2000)

[1.5] A. Rheinlander and H. Neumann, Physica Status Solidi (b), 64, K123 (1974)

[1.7] E. K. Sichel and J. I. Pankove, Journal of Physic and Chemistry of Solids, 38, 330 (1977)

[1.9] P. Buffat, J. P. Borel, Phys. Rev. A, 13, 2287, (1976)

[1.11] S. W. Chung, J. Y. Yu, J. R. Heath, Appl. Phys. Lett. 76, 2068, (2000)

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氮化鎵一維奈米線之合成與拉曼性質分析

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