氧硒化鋅合金的拉曼光譜研究;Raman spectroscopic analysis of ZnSeO alloys

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题名:	氧硒化鋅合金的拉曼光譜研究;Raman spectroscopic analysis of ZnSeO alloys
作者:	柯宏憲;Ke,Hong-hsien
贡献者:	物理研究所
关键词:	拉曼光譜;氧硒化鋅合金;ZnSeO alloys;Raman spectrum
日期:	2012-07-23
上传时间:	2012-09-11 18:40:54 (UTC+8)
出版者:	國立中央大學
摘要:	本論文所研究之氧硒化鋅合金，氧濃度分布於1.5%<x<11.6%。由光激發螢光光譜(PL)及壓電調製反射光譜(PzR)所量得之訊號能量位置隨著氧濃度增加的變化，符合能帶互斥理論，然而，高氧濃度樣品的XRD與PL訊號都有強度變弱且半高寬增加的現象，且高氧濃度樣品的PzR光譜並沒有觀察到微分訊號，這代表高氧濃度的氧硒化鋅晶格可能發生改變，因此本論文以激發波長為514.5nm與457.9nm的拉曼光譜，探討氧硒化鋅晶格隨著氧濃度上升發生的變化。透過類硒化鋅的LO聲子模態譜型分析得知，氧濃度小於2.7%的氧硒化鋅晶體，結晶品質是相當好的，當氧濃度大於5.3%以後，其應力已部分釋放，結晶品質會下降；而成分無序的程度隨著氧濃度的上升而增加，聲子相關長度減小，造成LO模態譜型的不對稱性增加。透過不同激發波長的拉曼光譜實驗得知，當雷射能量大於樣品能隙，滿足共振拉曼散射的條件時，多重LO聲子散射強度明顯增強。當氧濃度大於2.2%以後出現的OLVM1模態，隨著氧濃度的增加有藍移的趨勢。The oxygen concentrations of ZnSe1-xOx alloys studied in this thesis are in the range of 1.5%<x<11.6%. The results of photoluminescence (PL) and piezoreflectance (PzR) indicate that the relationship between bandgap and oxygen composition can be well described in the framework of band anti-crossing model (BAC model). However, the full width of half maxima (FWHM) of signals observed in XRD and PL become broader and the intensities become weaker in the higher O concentration range. These results indicate that the crystal structures may have changed. Thus we investigated the crystal structure via Raman spectrum. We found the crystalline qualities are quite good in low O concentration range from the analysis of LOZnSe lineshape. And compositional disorder increases with O content which leads to the shortening of phonon correlation length and asymmetric broadening of LOZnSe lineshape. From excitation wavelength dependent Raman spectrum, we found the signal intensities of multi-phonon scattering increase when the excitation energy above the band gap, which is the condition of resonant Raman scattering. The OLVM1 mode appears when O concentration are higher than 2.2% and blueshifts with increasing of O concentration.
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