氧化鎘鋅薄膜光學性質分析; Optical properties of ZnCdO thin film

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题名:	氧化鎘鋅薄膜光學性質分析;Optical properties of ZnCdO thin film
作者:	黃馨毅;Huang,HsinYi
贡献者:	物理學系
关键词:	氧化鎘鋅;拉曼;光激螢光;非諧和效應;生命期;ZnCdO;Raman;photoluminescence;anharmonic effect;lifetime
日期:	2013-07-19
上传时间:	2013-08-22 11:47:14 (UTC+8)
出版者:	國立中央大學
摘要:	本論文藉由光激螢光(PL)及拉曼散射光(Raman scattering)來分析鎘濃度0%至20%的氧化鎘鋅樣品之光學特性及晶格結構。由變溫光激螢光光譜可知，氧化鎘鋅擁有大量的局域態(localized state)，螢光訊號峰值隨溫度變化呈現S型(S-shaped)的現象。鎘的摻雜使氧化鎘鋅拉曼訊號半高寬增加，且呈現不對稱的情況，表示晶格振盪較為混亂，並有局限效應發生，造成選擇規則q=0的限制更為寬鬆。縱向光學聲子(LO phonon)訊號峰值位置與半高寬隨溫度變化關係可分析出非諧和作用力存在於氧化鎘鋅中，其與晶格熱膨脹及結構出現不規則排列有關。利用拉曼訊號半高寬與測不準原理可推算出光學聲子生命期，其分成衰變生命期τA與本質生命期τI，衰變生命期與非諧和效應相關，隨鎘濃度增加而變短；本質生命期反應出結晶品質的好壞，實驗結果顯示高濃度的本質生命期較長，結晶品質較佳，低溫螢光光譜訊號半高寬呈現的結果與此情況相同。 By using photoluminescence(PL) and Raman spectroscopy, we have studied the optical properties and crystal structure of Zn1-xCdxO (0%≦x≦20%) alloys. The localized states in Zn1-xCdxO were observed via the PL spectra that there will be an S-shaped shift in its temperature dependent PL peak. The line-width of Zn1-xCdxO in Raman signal has been broadened by the disorder of lattice vibration. The signal is asymmetric line shaped. This is described that there exists the confinement effect which leads to a relaxation of the q=0 selection rule. The temperature dependence of phonon line-width and peak position of LO modes are analyzed to be in terms of anharmonic effect induced by thermal expansion and compositional disorders. The lifetime of the phonons can be calculated according to the LO line-width and the energy-time uncertainty relation. It is composed of decay lifetime and intrinsic lifetime . The former lifetime is related to anharmonic effect, it decreases with the increment of the Cd content. The latter lifetime corresponds to the impurity, defects and isotopic fluctuation in the crystal quality. The experimented result indicates that high concentration of Cd in Zn1-xCdxO has better crystal quality and longer , we came up the same results in low-temperature PL line-width.
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