Preparation Of ZnO Films By Aqueous Solution Chemical Method At Low Temperature

Zinc Oxide (ZnO) is an important wide-bandgap semiconducting material in the photoelectric field. In this thesis, research on preparation of ZnO films using aqueous solution chemical method at low temperature was carried out in the growth system of Zn(NO₃)₂/HMT,Zn(NO₃)₂/NaOH,Zn(NO₃)₂/NH₃H₂O. Growth manner of the ZnO films in different system was analyzed, the effect of the process parameters, such as nature of the substrate, growth solution concentration, growth time, pH value, on the ZnO growth were systemically studied. In addition, the films as-prepared was eroded by ammonia solution to obtain films with new nanostructure.The results show that rod crystal grown from Zn(NO₃)₂/HMT system is c-oriented hexagonal wurtzite. The nucleation manner of the ZnO crystal is heterogeneous nucleation, and the growth manner of them was planar growth layer by layer. The dimension of the grown ZnO crystals had the same transformation trend with seed crystals on buffer layer. With the increase of the solution concentration, the diameter of the ZnO rod enhanced. Lath-like crystals were formed by prolonging the growth time to 48 h through secondary growth. When the [NaCl] varied from 0M to 0.1M, the average diameter of the ZnO crystals changed form 0.2μm to1.3μm. AcAc used as an assistant could play an important role in specific adsorption, leading to the formation of pyramid crystals through mild secondary growth.The rod crystal grown from Zn(NO₃)₂/NaOH,Zn(NO₃)₂/ NH₃H₂O systems are also c-oriented hexagonal wurtzite. The diameter of the ZnO rods from NaOH system was in the nano scale, while the rods from NH₃H₂O system varied in a large range because of the buffer effect of [Zn(NH₃)₄]²⁺. The pH value could affect the growth of ZnO films in the NH3H2O system. In alkaline growth solution, the proper growth temperature is 70⁹0℃, and the growth velocity can be changed by varied temperature.The erosion was not simply the inverse process of the crystal growth. The erosion process of the rod films could be described as pit erosion and cone erosion accordingly. Secondary growth of ZnO nanowires was obtained through dissolution-growth mechanism when the erosion process achieved the endpoint.