Study On The Fabricating Techniques And Characteristics Of ZnO Thin Films

Zinc oxide(ZnO)is an interesting wide band gap(3.3 eV at room temperature)â…¡-â…¥semiconductor material,which has a much larger exciton binding energy(60 mev)than GaN(～25 meV)and ZnSe(22 meV).ZnO has wurtzite structure,and its lattice parameters are a=0.3249 nm and c=0.5206 nm.ZnO possess excellence transparent conductivity,piezoelectricity,photoelectricity,gas sensitivity,voltage sensitivity,and they can be integrated with some semiconductor materials readily. ZnO films have many potential applications such as surface acoustic wave devices, planar optical waveguides,transparent electrodes,ultraviolet photodetectors, piezoelectric devices,varistors,UV-LEDs(light emitting diodes)and -LDs (laserdiodes)and gas sensors etc.ZnO is used to make UV-emitter and UV laser in the range of short wavelength,which play a very important role for improving light-noting density and accumulate-adopt vilocity of light information.Many different techniques such as sputtering,metal organic chemical vapor deposition(MOCVD),pulsed laser deposition,laser molecular beam epitaxy(LMBE), e-beam evaporation,spray pyrolysis,sol-gel,film oxygenation have been employed to fabricate ZnO films.Among numerous deposition techniques,PLD is a newly advanced film growth technique developed in recent years.Its advantages for fabricating ZnO films by PLD method are that the growth is easily controllable by changing the experimental parameters,and high quality films can be produced at lower growth temperature.We fabricate ZnO thin films with preferencel c-axis orientation by PLD method.The gowth procedure,characteristics and influence factors of ZnO thin films are discussed.The thin films with uniformity,compact and perfect c-orientation and good transparency in visible range have been obtained under optimum conditions.The structural and optical Characteristics of ZnO thin films were characterized by X-Ray diffraction(XRD)spectra,the atomic force microscopy(AFM)observations, the transmission electron microscopy(TEM)observations and photoluminescence(PL) spectra.The ZnO thin films have been fabricated on Si(111)substrate by pulsed laser deposition at growth temperature from 100℃to 500℃at a oxygen ambient pressure of 1.3 Pa.The results show that the thin film grown at 400℃has the most smooth surface and the most homogeneous crystal structure.Zinc oxide thin films have been grown on quartz substrates by pulsed laser ablation of a ZnO target in O₂ ambient at a pressure of 1.3 Pa at different deposition temperature.The structural and optical properties of deposited thin films have been characterized.The observation shows that the best obtained single crystalline thin films with hexagonal structure are that at growth temperature 500℃.The ultraviolet and blue emissions are observed by PL spectra.The results show that the crystalline quality and optical property of ZnO thin films is improved with increasing growth temperature.