Wet Chemical Preparation Of ZnO-based Transparent Conductive Films

ZnO is one kind of abundant and green materials, which has a direct band gap of3.37 eV and a high exciton binding energy of about 60 meV. ZnO films have excellent optoelectronic properties, which have potential application in solar cells, transistors and light-emitting devices. A variety of techniques such as magnetron sputtering, chemical vapor deposition and wet chemical preparations have been employed to prepare ZnO thin films. Among these techniques, wet chemical method is simple and capable of producing large-area films.In this dissertation, we mainly employ the sol-gel method and chemical bath deposition to prepare doped ZnO and multilayer thin films. The as-prepared film samples are characterized by XRD, SEM, XPS and UV-VIS spectrophotometer and four-point probe method. The main contents of this dissertation are as follows:(1) Firsly,after surveying the literatures, we briefly summarize the basic structure and optoelectronic properties of ZnO; meanwhile, the wet chemical preparations of ZnO thin films have been summarized in detail.(2) We prepared Si-doped ZnO(ZnO:Si)transparent conductive films by sol-gel method. UV irradiation or hydrogen reduction treatment significantly reduced the film resistance, the minmum sheet resistance was 1.6k?/□ and the optical transmittance of ZnO:Si thin films was higher than 80%.(3) We prepared CuO and ZnO/Cu O/ZnO thin films by sol-gel technique. Cu and ZnO/Cu/ZnO were formed with further H2 reduction of CuO and ZnO/Cu O/ZnO, respectively. Cu thin films were highly conductive with sheet resistance as low as 10 ?/□, while ZnO/Cu/ZnO multilayers were less conductive with sheet resistance of about 10 k?/□.The formation of large discrete Cu crystallites in the multilayers explains the poor electrical conductivity of the ZnO/Cu/ZnO multilayers due to poor wetting of Cu in ZnO.(4) We prepared ZnO:In thin films via chemical bath deposition, with the preferred orientation of the films varying from [002] to [100] and [110] by simply altering the solvent composition. The effect of deposition time, precursor concentration, bath temperature on the ZnO:In films was dicussed. Growth mechanism of the preferred crystallite orientation in ZnO:In thin films has been systematically investigated. It was found that the preferred orientation of the films is consistent with the fastest-growing crystallographic direction.