Preparation and Characterization of ZnO Films by Two-Step Electrodepostion

• Main Authors: Li-Ting Lin, 林麗婷
• Other Authors: 洪逸明
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/99516145437428899673

碩士 === 元智大學 === 化學工程與材料科學學系 === 97 === 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.