半導體奈米帶與奈米線之光譜研究
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2004
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我們探討三氧化二鎵奈米線、奈米帶、以及單一磷化鎵奈米線的表面結構、電性、與光譜特性，擴展先前群集奈米線的量測至奈米帶與單一奈米線的研究。
在三氧化二鎵奈米結構的研究中，首先，由全頻光譜的分析，我們發現11個紅外光活性振動模以及4個電子吸收帶，包括相近於塊材能隙的吸收峰。由拉曼散射光譜的分析，我們發現奈米帶的拉曼活性振動模與奈米線相近，並且沒有明顯的共振效應；隨著樣品的溫度升高，這些拉曼振動模的頻率往低頻偏移以及半高寬變寬，此變化的幅度與其他三五族半導體比較，顯得異常的小。
在單一磷化鎵奈米線的拉曼散射光譜研究中，我們發現其拉曼活性振動模與單晶相較之下，其頻率會往低頻偏移，並且形狀較為不對稱，我們以聲子侷限效應、雷射的熱效應、與電漿子耦合效應解釋此現象，並且發現電漿子耦合效應的模擬結果最能符合實驗結果。由偏振拉曼光譜的分析，我們發現入射光電場偏振方向與拉曼振動模強度之關係違背了馬勒斯定律，我們推測由於奈米線的直徑對長度之比值極小，這種結構的獨特性導致了異常的偏振拉曼光譜特徵。由偏振螢光光譜的分析，我們發現當入射光及散射光電場偏振方向與樣品長軸一致時，磷化鎵奈米線於2.16 eV處呈現一顯著的螢光訊號。
We present the local scanning probe microscopy and optical spectroscopic measurements of Ga2O3 and GaP nanostructures. By simultaneously mapping topography and electrostatic force on a surface, the local electrical properties of these nanomaterials can be correlated with their surface structure. Optical reflectance and transmittance spectra of Ga2O3 nanostructures reveal eleven infrared-active phonons and four electronic absorption bands. The phononic Raman spectra of Ga2O3 nanobelts are similar to those of nanowires. Interestingly, the resonant and temperature-dependent effects in the phonon response of Ga2O3 nanostructures are negligible as compared with other Ⅲ-Ⅴ semiconductoring nanowires . In addition, the peak shift and the broadening of the linewidth as well as asymmetric shape observed in LO phonon of isolated GaP nanowire agree with those calculated on the basis of the LO phonon-plasmon model. Moreover, the polarized Raman and photoluminescence (PL) spectra show strong angular dependence. The orientation dependences reveal maximum intensity of all Raman modes and PL excitation peak when the nanowire is aligned parallel to the polarization of the incident laser light.
We present the local scanning probe microscopy and optical spectroscopic measurements of Ga2O3 and GaP nanostructures. By simultaneously mapping topography and electrostatic force on a surface, the local electrical properties of these nanomaterials can be correlated with their surface structure. Optical reflectance and transmittance spectra of Ga2O3 nanostructures reveal eleven infrared-active phonons and four electronic absorption bands. The phononic Raman spectra of Ga2O3 nanobelts are similar to those of nanowires. Interestingly, the resonant and temperature-dependent effects in the phonon response of Ga2O3 nanostructures are negligible as compared with other Ⅲ-Ⅴ semiconductoring nanowires . In addition, the peak shift and the broadening of the linewidth as well as asymmetric shape observed in LO phonon of isolated GaP nanowire agree with those calculated on the basis of the LO phonon-plasmon model. Moreover, the polarized Raman and photoluminescence (PL) spectra show strong angular dependence. The orientation dependences reveal maximum intensity of all Raman modes and PL excitation peak when the nanowire is aligned parallel to the polarization of the incident laser light.
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奈米帶, 奈米線, 磷化鎵, 三氧化二鎵, 光學, 聲子, nanobelt, nanowire, gallium phosphide, gallium oxide, optical, phonon