研究生: |
林建豪 Chien-Hao Lin |
---|---|
論文名稱: |
硒化銦單晶之成長及光學特性研究 Growth and optical characterization of α-In2Se3 layer crystals |
指導教授: |
黃鶯聲
Ying-Sheng Huang 何清華 Ching-Hwa Ho |
口試委員: |
陳瑞山
Ruei-San Chen 趙良君 Liang-Chiun Chao 程光蛟 Kwong-Kau Tiong |
學位類別: |
碩士 Master |
系所名稱: |
電資學院 - 電子工程系 Department of Electronic and Computer Engineering |
論文出版年: | 2012 |
畢業學年度: | 100 |
語文別: | 中文 |
論文頁數: | 114 |
中文關鍵詞: | 硒化銦 、化學氣相傳導法 、熱調制技術 、六方晶系 |
外文關鍵詞: | In2Se3, chemical vapor transports method, thermoreflectance technique, hexagonal |
相關次數: | 點閱:465 下載:27 |
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本論文利用化學氣相傳導法 (Chemical Vapor Transport method,CVT)成長硒化銦系列晶體,目前成功成長出α-In2Se3層狀單晶, 之後進行晶體結構與光學特性分析。藉由能量散佈儀 (Energy dispersive X-ray spectrometer, EDS)量測可以確定成長材料之元素比與預期相符合。而利用X-ray晶格繞射 (X-ray diffraction, XRD)以及穿透式顯微鏡 (Transmission electron microscopy, TEM)分析可得到α-In2Se3為六方體系結構 (Hexagonal structure)且為Alpha結晶相。在光學量測上,α-In2Se3的近能隙傳導機制,可使用熱調制、壓電調制以及穿透實驗得出材料為直接能隙半導體且常溫300 K之能隙為1.453 eV,同時藉由溫度相依熱調制光譜之半高寬比變化量很小的結果可以推斷樣品應屬於缺陷型半導體,而缺陷主要是與Se空缺、In空缺以及In間隙等空缺相關型式存在。
α-In2Se3能隙以下的傳導訊號可以利用光導實驗來觀察到,而在高於能隙上之傳導訊號主要可以利用表面光電壓、表面光電導以及光致螢光光譜來觀察,這些高於能隙上的訊號推測是來自於樣品表面所生成之表面氧化態,其型式推測可能為α-In2Se3-3xO3x.
根據實驗結果驗證,這些低於能隙之缺陷態可以用來幫助吸收近紅外波段的能量,而高於能隙的能量則可利用樣品上的表面氧化態來輔助吸收,因此利用以上的實驗結果,實際應用上也製成光導型以及表面光電導型之原型光檢測器,利用此光檢測器之光導及表面光電導模式切換可以涵蓋近紅外至藍紫外光波段的檢測範圍。
Single crystals of α-In2Se3 were grown by chemical vapor transport method using ICl3 as a transport agent. X-ray diffraction and transmission electron microscopy (TEM) measurements confirmed hexagonal structure and alpha phase for the as-grown indium selenide layer crystals. Energy dispersive spectroscopy (EDS) analysis verified the stoichiometry of the α-In2Se3 compound.
The near-band-edge transitions of α-In2Se3 were characterized experimentally by thermoreflectance (TR), piezoreflectance (PzR) and transmission measurements. The experimental results confirmed that α-In2Se3 is a direct semiconductor with energy gap of 1.453 eV at 300 K. The broadening parameters of TR spectra do not change from 30 K to 300 K inferred that α-In2Se3 is a defect semiconductor with some vacancy-related defects (e.g. selenium vacancies, indium vacancies or In interstitials) inside the crystal.
Photoconductiviy (PC) measurement was used for characterization of defect transitions below band edge of indium selenide. The above band-edge transitions of α-In2Se3 have been evaluated by surface photovoltage (SPV), surface photo-conductive response (SPR) and photoluminescence (PL) experiments. The above band-edge transitions may come from surface oxidation states (α-In2Se3-3xO3x) existed on the α-In2Se3’s surface. The below-band-edge defect states facilitate the absorption of near-infrared (NIR) region and surface oxidation states absorb blue-to-UV portion. Based on our experimental results, the prototype of PC and SPR photodetectors of α-In2Se3 has been made, which shows promotion of optical absorption from NIR to UV range.
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