奈米氧化鋅結構之電化學研製及其在發光二極體之應用; Nanostructured ZnO prepared by electrochemical process and its application to light emitting diodes

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题名:	奈米氧化鋅結構之電化學研製及其在發光二極體之應用;Nanostructured ZnO prepared by electrochemical process and its application to light emitting diodes
作者:	黃茂嘉;Mao-chia Huang
贡献者:	材料科學與工程研究所
关键词:	陰極電鍍;氧化鋅;錫;奈米柱;銅;氯化鋅;雙氧水;氧化亞銅;發光二極體;cathodic electrodeposition;zinc oxide;tin;nanorods;copper;zinc chloride;light-emitting diode;cuprous oxide;hydrogen peroxide
日期:	2011-08-27
上传时间:	2012-01-05 12:24:57 (UTC+8)
摘要:	本論文採用定電位電鍍法，在純銅(99.9%)基板上分別析鍍具(002)優選方位之n-型摻錫氧化鋅奈米柱結構、p-型氧化亞銅、硫氰化亞銅等薄膜，或依序在銅基材上先電鍍一層氧化鋅緩衝層後，接著鍍上n-型摻錫氧化鋅奈米柱結構，然後是p-型氧化亞銅、硫氰化亞銅等薄膜，以製作n-型摻錫氧化鋅奈米柱結構與兩種不同p-型薄膜之Cu/ZnO/Sn-doped ZnO/Cu2O 或Cu/ZnO/Sn-doped ZnO/CuSCN異質接面，探討其作為發光二極體之可行性。研究之重點在於: 探討改變實驗參數對n-型摻錫氧化鋅奈米產物之形貌、結構與特性的影響。至於p-型氧化亞銅或硫氰化亞銅等奈米薄膜則大致依照文獻方法製備。定電位電鍍所得n-型摻錫氧化鋅奈米柱產物，經場發射掃描式電子顯微鏡(FE-SEM)結果顯示：固定氯化鋅濃度在1.96 mM、氯化錫濃度在0.04 mM、雙氧水濃度在2.45 mM時，若電位控制在 -0.20 V 與 - 0.50 V時，得到長方體奈米柱，電位在-0.90到-1.40 V得到含六方晶體奈米柱之薄膜。於 - 1.25 V析鍍出之六方晶奈米柱之平均柱徑約為120 nm。隨著溶液中雙氧水濃度增高至8.0 mM，奈米柱之柱徑增大至220 nm。由低掠角X光繞射分析(GIXRD)得知: 摻錫之氧化鋅奈米柱，以(002)為主峰，其峰值強度比純氧化鋅低且寬，顯示氧化鋅在摻雜錫後結晶細化；由螢光光譜分析(PL)結果顯示: 摻雜錫氧化鋅與純氧化鋅奈米柱相比，其能隙有紅移現象；經X光光電子能譜儀(XPS)分析得知: 摻錫氧化鋅奈米柱之化學狀態含有Zn-O的鍵結(鍵結能為1021.9 eV)和Sn-O的鍵結(486.7 eV)，顯示摻雜之錫離子為+ 4價，錫摻雜濃度為2 at%。由XPS縱深分析結果得知，本電鍍法所得摻錫氧化鋅之厚度隨著溶液中雙氧水濃度由2.45 mM增至8.00 mM，由150 nm增至250 nm。依據文獻在銅基材表面電鍍p型氧化亞銅薄膜之結果顯示: 在35℃於含CuSO4之鹼性溶液中，以-0.30 V電鍍20分鐘，獲得具有(111)優選方向之薄膜，膜厚約4.5μm，電阻率在1.35 Ω-cm。在含硫氰化物之若鹼性硫酸銅溶液於-0.90 V電鍍可獲得p-型硫氰酸亞銅薄膜，由EDX及UPS結果得知，此薄膜具有p型半導體特性。實驗所得之Cu/ZnO/Sn-doped ZnO/Cu2O 和Cu/ZnO/Sn-doped ZnO/CuSCN異質接面分別進行發光二極體的電流-電壓測試。結果Cu/ZnO/Sn-doped ZnO/Cu2O系統體有較大的漏電流出現，推測氧化亞銅與氧化鋅介面間缺陷較多所致。Cu/ZnO/Sn-doped ZnO/CuSCN系統之測試，顯示具有良好的二極體特性，當電壓達到8.00 V，電流密度可達致3.5 mA/cm2。 The 2 at.% Sn-doped ZnO nanorods with (002) preferred orientation were electrodeposited on a copper substrate (purity at 99.9%) in the present work. Influence of the H2O2 concentrations and deposition voltage on the microstructure and optical properties of the oxide film was of interest. Besides, we observed the influence of the doping of Sn4+ on the ZnO nanorods. At last, we fabricated the LED which used ZnO and ZnO:Sn nanorods as n-type layer. In this study, the Sn doped ZnO nanowires were successfully fabricated by electrodeposition and do not require any additional annealing process. According to the result, the hydrogen peroxide concentration is fixed at 2.45 mM, the change in voltage from the -0.2 ~ -1.40 V, the scanning electron microscope (SEM) shows that the surface structure consists of tetragonal nanorods into a polycrystalline thin film, and-1.25V results for the hexagonal nanorods, the average column diameter of about 120 nm, but not all the nanorods grow along the c axis, by changing the concentration of hydrogen peroxide that, when the hydrogen peroxide concentration of 8.00 mM of the nanorods is the best, column diameter of about 220 nm. By the grazing angle X-ray diffraction analyzer (GIXRD) results that, compared to pure zinc oxide nanorods, the (002) peak decreased and broadened by doping 2 at.% Sn, reducing the crystalline. The Sn-doped ZnO film displays the energy band gap a little red-shift as compared to pure ZnO film by photoluminescence results. the X-ray photoelectron spectroscopy (XPS) analysis of the Zn-O bonding (binding energy of 1021.9 eV), Sn-O bond was 486.7 eV, that the number of tin valence 4 +, and by the composition analysis of zinc and oxygen ratio of about 1:1, doped tin about 2 at%. By the etch-depth analysis that, with the hydrogen peroxide concentration from 2.45 mM to 8.00 mM, 150 nm film thickness increased by 250 nm. By cathodic electrochemical method on 99.9% pure copper substrate surface to growth of p-type cuprous oxide film, the experimental results showed that when the deposition temperature is 35 ℃, the film has a high degree of preferred orientation (111), and the film thickness of about 4.5 μm, resistivity of about 1.35 Ω-cm. The cuprous thiocyanate films by electrodeposition of -0.90 V, this film has a p-type semiconductor characteristic by ultraviolet photoelectron spectroscopy (UPS) and energy dispersive x-ray analysis (EDX) analysis. According to the I-V result, the Cu2O/ZnO-based diodes with large leakage current density, it is difficult to speculate oxide combined with oxides, resulting in interface voids, defects making poor diode characteristics. The ZnO-based/CuSCN diodes with small leakage current density and all have good diode characteristics, because oxides and organic compounds easier to combine. If we as a buffer layer of ZnO, the formation of ZnO / Sn-doped ZnO / CuSCN of the heterojunction, we can see the whole of the current density increased, and when the voltage reaches 8.00 V, the current density to achieve 3.5 mA / cm2.
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