Research On Preparation And Properties Of Metal-doped Zinc Oxide Films

Zinc Oxide is an n type semiconductor material which has wide band gap with high thermal stability and chemical stability.The Zinc Oxide film has good electrical conductivity and high transmittance in the visible light area,which makes it widely use in optical and magnetic storage devices,light-emitting diodes,solar cells(transparent conducting electrodes),sensors,surface acoustic wave devices and chemical devices.Changing deposition parameters,ZnO films and metal doped ZnO films are prepared by magnetron sputtering.X ray diffraction(XRD),scanning electron microscope(SEM),and energy dispersive X ray diffraction(EDX),the UV-vis-near-infrared(UV-VIS-NIR)spectrophotometer and four probe resistance tester were used to study the structure,surface morphology,composition,optical properties and electrical properties of the films.Firstly,ZnO films with different deposition parameters are prepared on Si(100)substrate by RF magnetron sputtering.The XRD patterns show that all ZnO films had good crystallinity and grow along(002)direction preferentially.Considering the crystallinity of the film,the optimum preparation conditions are obtained as follows:sputtering power is 100W,work pressure is 1.2Pa,argon oxygen ratio is 20:1,the substrate temperature is 400 C and the deposition time is 1.5h.For the ZnO film deposited under the optimum conditions,the resistivity measured by four probe method is 25.6?·cm.The SEM measurement shows that the grain size is 34.1nm,which is in accordance with the result of XRD calculation.The surface roughness of the ZnO thin film prepared under the optimum preparation conditions is 21.9nm.The visible transmittance of ZnO films measured by UV-VIS-NIR spectrophotometer is 84.7%and the average reflectivity is 25.7%.Secondly,under the optimum preparation conditions,by using the RF and DC magnetron co-sputtering method,the doped ZnO films with different doping concentrations are prepared by changing the sputtering power of the doped target.The dopant metals are yttrium(Y),vanadium(V)and copper manganese alloy(Cu-Mn).The XRD patterns of the doped Zinc Oxide(M:ZnO)are presented.The thin film has only ZnO diffraction peak,indicating that the metal is successfully doped into the lattice of ZnO film.The EDX patterns show that the doping concentration of ZnO films increases with the increase of doping power.With the increase of the doping power,the grain size of the ZnO film increases and the crystallinity increases.Compared with the undoped ZnO film,the doped ZnO thin film is coarse.As the power increases,the roughness increases with the increase of power.The doping of Y makes the transmittance of ZnO films increase in visible light area than that of the undoped Zinc Oxide film,with an average transmission rate of 85.3%.For V and Cu-Mn doping,the transmittance of ZnO films in the visible light region decreases gradually with the increase of doping power.The average reflectivity of the ZnO film in the visible light region increases with the doping of Y,and the average reflectivity of the V-doped ZnO films is maintained at the reflectivity level of the undoped film in the visible light region.When the V doping power is 60W,the reflectance is obviously lower than the undoped sample.The Cu-Mn doping makes the film reflectivity drop,and the maximum reflectivity is no more than 20%.The resistivity of ZnO thin films measured by four probe method indicates that Y,V,and Cu-Mn doping are beneficial to improve the conductivity of the film.The lowest resistivity of 19.3,18.7 and 17.6 ?·cm at the maximum doping power is obtained,respectively.