以化學浴沉積法成長穩定形貌結構之氧化鋅奈米柱及其發光特性之研究

Stable morphology and luminescent property of ZnO nanorod fabricated by chemical bath deposition

郭謹瑞(Jin-Ruei Guo)

指導教授 ： 温武義

中原大學/工學院/電子工程研究所/碩士(2015年)

https://doi.org/10.6840/CYCU.2015.00228

摘要

本研究主要利用化學浴沉積法成長氧化鋅奈米柱，藉由有系統的調整製程參數，歸納出各成長環境下所成長之奈米柱表面形貌，以製備出方向性一致且口徑小於100nm之氧化鋅奈米柱，並分析其紫外光波段之發光特性，探討各成長參數對於發光特性之影響。首先利用濺鍍法於矽基板(111)上成長ㄧ層氧化鋅晶種層，再運用化學浴沉積法於氧化鋅晶種層上成長氧化鋅奈米柱，透過改變成長溶液濃度、成長溫度、成長時間，可製備出不同形貌之氧化鋅奈米柱，其發光特性也隨調整的參數而有不同變化。
利用化學浴沉積法於晶種層上所成長的氧化鋅奈米柱在X光繞射(XRD)量測下具有相當顯著的(002)面晶相訊號，亦可藉由掃描式電子顯微鏡(SEM)觀察確認六角柱狀形貌。藉由SEM量測的結果可發現，隨著反應溶液濃度的提升，氧化鋅奈米柱的口徑有逐漸變大且彼此熔合成薄膜狀的趨勢。隨著化學浴成長溫度之上升，奈米柱間的間隙會逐漸變大，單位面積內的奈米柱密度降低且呈現傾倒狀。隨著化學浴成長之時間增加，氧化鋅奈米柱之柱高及口徑皆會逐漸變大。最後藉由降低反應溶液濃度至0.025 M且控制成長時間至3小時及成長溫度至65℃，可製備出平均口徑小於60 nm之氧化鋅奈米柱。
室溫光激螢光(PL)量測的結果顯示出，於光子能量約為3.29 eV之紫外光波段處皆有明顯的自由激子所致發光。低溶液濃度下所成長之奈米柱，其發光強度比高濃度所成長者高且半高寬也較窄。增加成長時間所製備出之氧化鋅奈米柱，在低溫成長環境(65℃)下，自由激子之發光強度與成長時間成正比；而高溫成長環境(95℃)下則呈現相反趨勢變化。低溫(5K)PL量測下，可觀察出在光子能量為3.37eV波段處之發光主要為施體束縛激子所造成，透過multiple Guassian fitting，可辨別出游離施體束縛激子(D^+ X)及中性施體束縛激子(D^0 X)分別於3.372及3.357 eV之發光位置，另外於3.323 eV可發現一強度較弱的TES(D^0 X)發光。最後再透過變溫PL量測，可得知游離施體束縛激子相對於中性施體束縛激子，在升溫時發光強度急遽下降的現象。

關鍵字

化學浴沉積 ； 奈米柱 ； 氧化鋅 ； 光激螢光

並列摘要

In this study, we plan to fabricate ZnO nanorod via chemical bath deposition. Through adjust the growth parameters systematically, the morphology and luminescence properties of ZnO nanorods grown under different conditions can be summarized. Finally, the well-aligned nanorods with it’s average diameter is smaller than 100 nm can be fabricated. First of all, a thin ZnO seed layer was sputtered on a silicon substrate (111) and then the ZnO nanorods were fabricated by chemical bath deposition. By changing the solution concentration, growth temperature and growth time, ZnO nanorods with different morphologies can be obtained. Besides, the luminescence property of ZnO nanorods change with different growth parameters.
The ZnO nanorods grown by CBD show’s an evident (002) face signal under X-ray diffraction (XRD). The hexagonal structure can also be presented by the top-view SEM images. By scanning electron microscopy (SEM) measurement, we can figure out that the diameter of ZnO nanorod gets larger and then gradually become a film-like structure while increasing the solution’s molar concentration. With the growth temperature increase, the oblique morphology makes the space of nanorods more wider and further let the density of nanorods decrease. The increase of growth time will make the length and diameter of nanorods more longer and larger. Finally, the ZnO nanorods with the average diameter which is smaller than 60 nm were obtained by decreasing the solution concentration to 0.025 M, fixing the growth time in 3 hours and growth temperature at 65℃.
The room temperature photoluminescence (RT-PL) measurement shows a strong UV emission intensity at about 3.28 eV which is attributed to the recombination of free exciton (FX). The nanorods grown under low concentration shows a strong FX intensity and narrow full width at half maximum (FWHM). Under 65℃, the FX intensity increase with the growth time. However, the trend of FX intensity is reverse under 95℃. Furthermore, the low temperature (5K) photoluminescence (LT-PL) measurement shows a strong emission of donor-bound exciton (D^0 X) at 3.37 eV. By using multiple Guassian fitting, we can recognize the main emission band includes two different luminescence peak which are attributed to the ionized donor-bound exciton (D^+ X) and neutral donor-bound exciton (D^0 X) at 3.372 eV and 3.357 eV, respectively. Also, a weak TES(D^0 X) emission is found at 3.323 eV. Under temperature dependent photoluminescence measurement, the emission intensity of D^+ X drop abruptly than D^0 X does while the temperature increase.

並列關鍵字

ZnO ； chemical bath deposition ； nanorod ； photoluminescence

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