利用兩階段電沉積法製備氧化鋅薄膜及其性質研究

Preparation and Characterization of ZnO Films by Two-Step Electrodepostion

林麗婷(Li-Ting Lin)

指導教授 ： 洪逸明

元智大學/工程學院/化學工程與材料科學學系/碩士(2009年)

https://doi.org/10.6838/YZU.2009.00124

摘要

本研究於氯化鋅(zinc chloride, ZnCl2)及氯化鉀(potassium chloride, KCl)水溶液中，通入一穩定流量氧氣，以兩階段恆電位電沉積(electrodeposition)的方式，於ITO(indium tin oxide)導電玻璃基材上製備氧化鋅(zinc oxide，ZnO)薄膜。於兩階段電沉積法中，先於ITO基材上沉積一層晶種層，而後再於晶種層上生長出氧化鋅。其沉積第一階段晶種層之目的為降低第二階段生長氧化鋅時所需的活化能，提高生長效率，並且藉由晶種層的分佈密度與晶種的大小分佈，進而控制氧化鋅薄膜之表面生長型態。藉由改變電沉積法的反應條件，探討晶種層沉積之反應溫度、鋅離子前驅物濃度、反應電壓與反應時間等變數，對氧化鋅晶種層之表面型態與光學性質之影響，並進而探討其對氧化鋅薄膜之成長型態、結構與性質的影響。
研究結果顯示：使用單一階段電沉積法於ITO基材上沉積氧化鋅時，所沉積之氧化鋅其表面型態無均一性且為雜亂生長，其型態包括柱狀、顆粒狀與板狀結構。而利用兩階段之電沉積反應，經由改變反應條件沉積之氧化鋅晶種層作為基材，所得之氧化鋅薄膜，皆可於基材上生長出氧化鋅棒狀結構，且由XRD分析顯示為多晶且具(002)之優選取向的薄膜。
當改變反應溫度沉積所得之晶種層，其結果顯示：反應溫度提高，可促進晶種生長，使其生成密度增加，而晶種層之表面高度全距(Rmax)與粗糙度(rms)隨反應溫度之上升而增加。將不同反應溫度沉積之晶種層為基材，所得之氧化鋅薄膜的結晶型態為棒狀結構，且氧化鋅棒與與晶種之生成密度有相同趨勢，而反應溫度提高亦有助於氧化鋅棒朝c軸方向成長。當以55 ℃之反應溫度沉積之晶種層為基材，所得之氧化鋅棒，直徑分佈主要於150 nm左右，於(002)之優選取向的織構因素(texture coefficient，TC)為2.26。
當以鋅離子濃度作為操作變因時，成核密度與鋅離子濃度的大小成正比關係，且經由第二階段成長反應後，在第一階段濃度
0.001 M的條件下所沉積之ZnO的型態最為均一化，其棒狀直徑在150 nm左右佔總數之82 %，透光率較佳，且有(002)方位之優選取向，其TC值為2.26。
當反應電壓由-0.6 V提升至-1.0 V，沉積之晶種的生成密度增加，且晶種層之Rmax與rms值下降，分別由867.3 nm下降至157.9 nm與116.3 nm下降至23.9 nm。當以較高反應電壓沉積之晶種層作為基材，所得之氧化鋅薄膜，其表面型態為由棒狀型態之氧化鋅緊密排列而成的緻密薄膜，因此其薄膜透光率與(002)方位的優選取向較佳，其TC值最高達3.22。
藉由不同之沉積時間所沉積之氧化鋅晶種層得知，隨沉積時間之增加，由於晶種將ITO上之空隙填滿，因此晶種層的Rmax與rms降低。當沉積晶種層之時間由5 min至10 min時，其rms由80.7 nm下降至25.3 nm，Rmax則由554.2 nm下降至213.9 nm，但由於晶種層厚度的增加，使薄膜透光率下降。

關鍵字

氧化鋅 ； 兩階段電沉積 ； 薄膜

並列摘要

In this paper, the large-scale ZnO films were prepared onto ITO glass substrate via a two-step electrodeposition method from an aqueous solution. The electrodepositon device was carried out in a three electrodes system, in which the ITO glass was used as the working electrode and the electrolyte contained ZnCl2 (zinc chloride) and KCl (potassium chloride) aqueous solution which bubbled with oxygen. The first and second-step electrodeposition were played roles to deposit homogeneously ZnO seed layers and grow ZnO films respectively. The effects of electrodeposition conditions of ZnO seed layers, such as temperature, concentration of zinc ion, potential and deposition time on the nucleation process and diameter, morphology and properties of ZnO films were discussed.
These results showed that the morphology of ZnO was ununiform and contained rods, grains and plates by one-step electrodeposition. No matter which the electrodeposition factors of seed layers that were changed, the morphology of ZnO films were rods and obtained strong preferential orientation along the (0002).
To study the effect of electrodeposition temperature of seed layers, the temperature increased could accelerate growth of nucleus that enhancing the density on ITO substrate, but the surface altitude difference (Rmax) and roughness were decreased. The ZnO rods were oriented along the c-axis with increasing the temperature of electrodeposition of seed layers. When the temperature was 55 ℃, diameter distribution of ZnO rods was narrower than other temperature that almost distributed at 150 nm and the texture coefficient (TC) of (002) was 2.26.
To study the effect of zinc ion concentration of seed layers, it was found that the density of seed was proportional to the zinc ion concentration. ZnO films deposited on ZnO seed layers which electrodeposition at 1×10-3 M of zinc ion concentration had uniform diameters and higher transmittance.
When the reaction potential was increased from -0.6 V to -1.0 V, the growth density of nucleus was increased, however Rmax and rms decreased from 520.18 nm to 157.92 nm and 116.31 nm to 23.9 nm respectively. The morphology of ZnO films deposited on ZnO seed layers which electrodeposition at higher potentials was formed by compact rods, therefore the preferential orientation of (002) and transmittance of the film were higher than other conditions.
When deposition time of seed layers was increased from 5 min to 10 min, the Rmax and rms were respectively decreased that from 554.23 nm to 213.90 nm and 80.7 nm to 25.3 nm. However, the thickness of buffer layer was increased, and the transmittance was decreased.

並列關鍵字

zinc oxide ； two-step electrodeposition ； film

參考文獻

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