Preparation And Characterization Of ZnO Thin Films

Zinc oxide thin film is one kind of direct band gap semiconductor materials (E_g=337eV at RT) with a high exciton binding energy of about 60 meV.It has high transmittance for the visible light and high absorption for ultraviolet.Therefore,it was considered to be a new photo-electric material in shortwave length as GaN.It can be used to fabricate display,window materials for solar cells,surface acoustic wave devices,luminescence diode and voltage varistors.Recently,ZnO thin film attracts much attention in semiconductor materials research field.There are many methods used to deposit ZnO thin film,such as magnetron sputtering,chemical vapor deposition(CVD),pulsed laser deposition(PLD), metal-organic chemical vapor deposition(MOCVD) and molecular beam epitaxy (MBE).However,the sol-gel method has the advantage of simple equipments,and it is easy to be doped of atomic class and can prepare large area films on various substrates.In this paper,the zinc oxide thin films were prepared on glass by sol-gel process from 2-methoxyethanol solutions prepared by Zinc acetate as precursor,DEA as stabilizer.The effect of process condition such as pre-annealing temperature, annealing temperature,annealing time,annealing atmosphere,concentration of Zn²⁺ and layers on the structure and optical transmittance of the films was studied by X-ray diffraction(XRD) and UV-visible spectrophotometry.The optimum technological parameters for the best properties of ZnO thin films on the glass substrate were that the pre-annealing temperature was 350℃,the annealing temperature was 600℃,the annealing time was 2 hour,the annealing atmosphere was air,the sol concentration was 0.4 mol/L.The zinc oxide thin films with high c-axis orientation and optical transmittance were also prepared on silicon wafer by sol-gel process,on the base of silicon wafer research and the optimum technological parameters.Fluorescence spectrophotometer was also used to excitated the ZnO films at room temperature for the further research of the material.The growth mechanism of ZnO thin films in the different process of sol-gel method and the special phenomena in the experiments were discussed at last.