Study Of Structural And Optical Properties Of ZnO Thin Films Prepared By Sol-gel Technique

ZnO is a novel wide direct-gap semiconductor. It has great uses in information age. Compared with GaN, high-quality ZnO thin film can be synthesized at much lower temperature. ZnO has higher excitonic bingding energy (60meV) ,which promises strong photoluminescence from bound excitomic emissions at room temperature. It can be used to fabricate emiting diode, short wavelength lasers ,display devices, high-speed optical switch and optical detector. Therefore, ZnO thin film attracts as much attention in photoelectric research field.ZnO, AZO and Mg_xZn_1-xO thin films were prepared on Si (111) and glass substrates by the sol-gel process. The effects of sol system, heating processs, impurity concentration and excitation wavelength were investigated. The process of ZnO films highly oriented along c-axis and optical property were focused on. After investigation and analysis of the samples by XRD, the growing parameters were optimized. High-oriented ZnO film with XRD FWHM of 0.36° was obtained at Si (111) substrate: 0.35mol/1 (Zn²⁺) ,96 h (aging time) ,250°C (preheating temperature) ,700°C (annealing temperature) and two hours(heating time) . The surface morphology showed well-proportioned hexagonal grains indicated by atomic force microscope (AFM).Optical transmittance of ZnO films on glass substrates were investigated. The optical transmittance spectra of the films showed a transmission between 77 and 87% in the visible light region and the bandgaps were basically equal to bulk ZnO. Fluorescence spectrophotometer was used to excitated the ZnO sumples at room temperature. Photoluminescence spectra showed a better UV emission of 395nm and a little blue-green emission. Compared with ZnO, there was no change of the UV peaks location in AZO and the emission peaks had a shortwavelength shift in Mg_xZn_1-xO films.