Synthesis and Characterization of Ga-doped ZnO Nanorod Thin Film

• Main Authors: Hsiang-Yu Chang, 張湘瑜
• Other Authors: Dong-Hwang Chen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/51026149666829912566

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === Abstract This thesis concerns the synthesis and character-ization of Ga-doped ZnO nanorods. Firstly, ZnO seeds were synthesized by sol-gel method and spin-coated on the surface of ITO substrate. Then, Ga-doped ZnO nanorods were grown on the seed layer along the C axis via hydrothermal technique. The effects of Ga-doping concentration on the morphology and the optical and electrical properties were investigated. Doping Ga into ZnO lattices was expected to modulate the energy bandgap and increase carrier concentration of ZnO semiconductor for the applications in photoelectro-chemical devices or solar cells. The resultant ZnO nanorods were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to observe their morphology. Their crystalline structure and optical properties were characterized by X-ray Diffraction (XRD), photoluminescence (PL), and UV/VIS spectro-photometer. The results revealed that the crystallinity obviously decreased and the UV emission peak was blue-shifted after Ga doping. From the HRTEM and XPS analyses, it was demonstrated that Ga atoms were really doped into the ZnO lattices. In order to know the characteristics of Ga-doped ZnO nanorods, four-point probe station was used to measure their conductance. After that, Schottky contact was made by contacting Pt to Ga-doped ZnO and a three-electrode electrochemical system was employed to observe the performance of Ga-doped ZnO in a photoelectrochemical cell. The conductance measurement revealed that the conductance decreased when the doping concentration increased. This might be due to the defect inside the lattice resulted by Ga doping. From the I-V (current-voltage) relation of the Schottky contact and photoelectro-chemical cell, there existed an optimum doping concentration (about [Ga] = 0.5%) to enhance the current. Because energy bandgap and carrier concentration were two main factors to affect magnitude of current density, the opposite current behaviors of Ga-doped ZnO nanorods appeared as the Ga concentration increased. Thus, the different doping level would induce the different influence on the current density.