摻2 at.% 錫氧化鋅奈米管陣列之電化學製備及其結構與特性探討;On the array of 2 at.% Sn-doped ZnO nanotubes prepared by electrochemical deposition with their structure and characterization

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Title:	摻2 at.% 錫氧化鋅奈米管陣列之電化學製備及其結構與特性探討;On the array of 2 at.% Sn-doped ZnO nanotubes prepared by electrochemical deposition with their structure and characterization
Authors:	黃聖壹;Huang,Sheng-Yi
Contributors:	機械工程研究所
Keywords:	選擇性蝕刻;奈米管;電化學沉積;氧化鋅;摻錫氧化鋅;奈米柱;nanorods;Electrochemical deposition;Sn-doped ZnO;ZnO;Selective etching;nanotubes
Date:	2012-07-05
Issue Date:	2012-09-11 18:16:33 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文之研究目的在製作氧化鋅和摻錫氧化鋅之奈米柱、奈米管陣列，並探討其結構與性質之關係。以定電位電化學析鍍法在銦錫氧化物(Indium-Tin Oxide, ITO)玻璃基材上，自含雙氧水氯化鋅鍍浴與外加氯化錫之另一鍍浴中分別成長出不同形貌之奈米柱陣列。由掃描式電子顯微鏡(Field-Emission Scanning Electron Microscope, FE-SEM)觀察顯示: 尖頂之摻2 at.% 錫氧化鋅較平頂之純氧化鋅奈米柱細長(直徑250 nm < 300nm；高度1850 nm > 900 nm)且呈密集陣列。經低掠角X光繞射儀(Grazing Incident X-ray Diffraction, GIXRD)分析兩種奈米柱陣列晶體結構皆屬於(002)面優選之六方堆積纖維鋅礦(Wurtzite)，摻錫氧化鋅之(002)面訊號則比純氧化鋅稍弱；紫外-可見光光譜儀(UV-Visible Spectrometer)量測顯示摻錫氧化鋅平均穿透率較氧化鋅奈米柱下降約2 %(但仍維持在88 %之高透光率)；摻錫後使氧化鋅能隙值降低約0.08±0.01 eV；光致螢光光譜儀(PL Spectrometer)分析得知: 摻錫氧化鋅之本質發光有紅移現象(由383 nm 偏移至388 nm)。X光電子能譜儀(X-ray Photoelectron Spectrometer, XPS) 鑑定試片表面顯示: 摻錫氧化鋅奈米柱化學狀態為SnO2(屬於四價錫)之鍵結，Sn4+摻雜至氧化鋅中將有利於提供額外電子來改善陣列之電阻率。從四點探針(Four-point probe)量測到的片電阻值進一步證實摻雜錫之氧化鋅較純氧化鋅奈米陣列之電導性質更佳(片電阻值降低了約三個冪次)。由表面輪廓儀 (Alpha step)的分析發現: 摻錫氧化鋅奈米柱之表面平均粗糙度(Ra)較純氧化鋅奈米柱增加了43 %。採用鹼性化學蝕刻進行選擇性蝕刻，將上述兩種奈米柱陣列製作成相對應之奈米管陣列，並經由上述儀器分析得知: FE-SEM觀察結果顯示不論氧化鋅或摻錫氧化鋅奈米管均具有直徑約150 nm之六角形孔洞。GIXRD分析結果發現:兩種氧化鋅奈米管的(002)面峰值強度均隨蝕刻時間之增長而降低。PL分析結果則顯示: 兩種奈米管陣列缺陷發光(450 ~ 600 nm)之強度皆隨蝕刻時間之增長而提升。且摻錫樣品同樣有本質發光紅移現象。XPS鑑定結果則與前述奈米柱試樣一致。四點探針(Four-point probe)量測到的兩種奈米管之片電阻值稍增加。Alpha step的分析發現:氧化鋅及摻錫氧化鋅奈米管蝕刻後Ra值分別增加了63 %及52 %。In this thesis, the ZnO nanorod array were deposited on the transparent conductive substrates by the electrochemically deposition without pre-depositing any seed layers, in order to further improve the electrical properties of ZnO nanorod array, Sn4+ ions were introduced into the ZnO nanostructures, moreover the wet etching were chosen for fabricating the hollow ZnO and Sn-doped ZnO nanotubes though to the selective etching mechanism. The produced ZnO/Sn-doped ZnO nanostructures were characterized by field-emission scanning electron microscope, grazing incident X-ray diffraction, photoluminescence spectrometer, UV-visible spectrometer, alpha step, four-point probe and X-ray photoelectron spectrometer.From the experimental results, the ZnO and Sn-doped ZnO nanorods deposited at constant cathodic potential of -1.00 V reveal integrally hexagonal wurtzite structure, after addition of the Sn, the shape of the nanorods change from the flat top into a sharp pointed top and the diameter also decrease from 300 nm to 250 nm, furthermore the density between nanorods become more dense. It can be seen that the etching time of 60 minutes resulted in a hexagonal pit with 150 nm inner diameter on the center of both ZnO and Sn-doped ZnO nanotubes. It also found that a 43% increase in surface roughness(Ra) due to the doping of Sn, moreover 63% and 52% increase for ZnO/Sn-doped ZnO nanotubes, this results indicate that the surface texturing of ZnO and Sn-doped ZnO nanotubes structures were successfully achieved by wet etching.Analysis by grazing incident x-ray diffraction(GIXRD), All ZnO nanorods samples are polycrystalline with hexagonal wurtzite structure and exhibited the highest intensity on the (002) crystal plane which indicated the preferred orientation, neither metallic zinc or tin characteristic peaks nor tin oxide peak was observed from the XRD patterns. The intrinsic emission peak from ZnO was shift from 383 nm to 388 nm due to changes in carrier concentration caused by doping Sn, furthermore the broad, higher intensity visible emission were observed after doping Sn and wet etching, it originating from the increasing of defects density in Sn-doped ZnO nanorods or nanotubes. The Sn-doped ZnO samples have 88% average transmittance in visible region but still 2% behind the undoped ZnO samples which is attributed to the changes of grain size. The band gap of Sn-doped samples has 0.09 eV decrease according to the changes in carrier concentration. Concerning the XPS spectrum of Sn3d5/2 peak was located at 486.5 eV which indicates that this binding energy was attributed by Sn4+ ion doping, besides the sheet resistance of Sn-doped samples measured by four-point probe have a thousand times decrease which confirmed that the goal for improving the electric properties of ZnO has been achieved.
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