Electrodeposition And Morphologies Control Of CuX(X=Br, I)

The copper halides have attracted intensive interest in the past decades. This is because they are prototype materials for nonlinear optical research and exhibit many unusual properties, such as large band gap,negative spin-orbit splitting, unusually large temperature dependency, and analogous diamagnetism behavior. Copper(I) bromides have been used as catalysis in organic synthesis, batteries, gas sensors and lasers. Copper(I) iodines have potential applications in superionic conductor, solid-state solar cells, catalysis for synthesis of organic compounds, etc. Therefore, it is important to study the preparation of CuBr and CuI crystals. Electrodeposition is a well known solution process that can be applied in the growth of semiconductor films from aqueous or nonaqeous solutions. The advantages of electrodeposition compared with other techniques include low process temperature, low cost and capability of controlling grain size, morphology and chirialty of the deposited films. In this paper, the high purity and good crystallinity CuBr and CuI crystals have been obtained through electrodeposition, their morphologies have been tuned by changing solution pH, temperature, applied potentials or the additions of amino acids.Preferred orientations of films have been one of the central topics in the crystal growth community. Here the growth methanism of the (111) preferred orientations of the CuBr film was analyzed. The preferred orientaion was influenced by three factors: electrocrystalline conditions, substrate and surface free energy of the deposits. The study showed that the influence of the deposit conditions such as pH, deposit potential, deposit time and temperature could be neglected. And the influence of the substrate could also be omitted, for it is a polycrystal. Therefore, the factor lead to the preferred orientation of the CuBr film is the surface energy. Since (111) plane of CuBr possesses the lowest surface energy for the crystal with fcc structure, it is easy to nucleate and grow on this face. CuBr films with different crystal orientations and morphologies were prepared by an electrodeposition method with L-Hisitine and glycine as additives. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectra and photoluminescence spectra (PL). The experimental results show that when L-Hisitine was added, the prefered crystal orientations of the as-prepared CuBr films have been weakened largely. And the morphologies of CuBr have been changed from octahedral to uniform microspheres aggregated by sheet-like structures with the mean diameter about 4μm. However, glycine has negligible effect on the morphologies or orientation of CuBr films in our experiment. The crystal growth mechanism of the CuBr films prepared by the electrodeposition method with different amino acids as additives was preliminarily studied. The effects of histidine concentration,deposition temperature and deposition voltage on morphologies of CuBr were also investigated.CuI crystal with high purity and highly (111) orientation was prepared by one-step electrodeposition using EDTANa-2 as complexing agent. This preferred orientation was beneficial to control the concentration of iodine related traps. Therefore, good fluorescence properties were obtained. It favors to improve stability of the photoelectric property and results of larger utilization spatial. The effects of depositon time,pH and deposition temperature on crystal growth of CuI were investigated furthermore. The results showed that the three factors could not change preferred orientation of CuI. The deposition temperature influenced slightly on morphologies.