| As a wide band gap semiconductor,transparent conductive oxide(TCO)thin film was investigated in the early 19 th century.Since the TCO thin film has relatively good optical and electrical properties,it is widely employed as transparent electrodes in optoelectronic devices such as sensors,flat panel displays and solar cells.Zinc oxide(Zn O)is abundant,cost-effective and non-toxic,so it is becoming a dominant position in the TCO thin film in recent years.At present,much attention has been paid on improving the optical and electrical properties for single element doped Zn O thin film,yet codoping with two elements,especially the study on Ti and Ga doped Zn O(GZO:Ti)thin film is relatively absent.Therefore,we choose transparent conducting GZO:Ti thin film as the study object in this paper.In this paper,radio-frequency magnetron sputtering technology was used to sputter GZO:Ti thin films on 37.5 mm×2.5 mm×1.1 mm glass substrates under different deposition temperature,argon pressure,sputtering power and target-substrate distance.The microstructure,electrical and optical properties of the samples were studied by XRD,XPS,SEM,UV-visible spectrophotometer and four-point probe,respectively.The main works and conclusions are shown as follows:(1)The optoelectronic properties of the deposited thin films were quantified by means of figure of merit.Based on the measured transmission curve,the average transmittance in the visible region of the GZO:Ti thin films was calculated.And the optical band gap was also estimated using the extrapolation method.According to the results of figure of merit(?),in addition,a set of optimal process parameters for preparing GZO:Ti thin films was obtained in this paper.The maximum ? value is observed to be 4068.9 ?-1·cm-1.(2)Process parameters have significant effect on the microstructure of thin films.According to the XRD results,diffraction peak appears in(100),(002)and(004)for all the deposited thin films.The orientation degree of(002)is more than 97.1%,so GZO:Ti thin films have a better growth in(002)direction.The experimental data shows that the deposition temperature,argon pressure,sputtering power and target-substrate distance significantly affect the average grain size(D)and compressive stress(?)of thin films.The values of D and ? are 38.2~85.7 nm and 0.226~0.443 GPa,respectively.(3)Process parameters have different effects on the optical property of thin films.The results shows that deposition temperature,sputtering power and target-substrate distance can change the average transmittance in visible region(Tav)and optical band gap(Eg)of thin films.However,the average transmittance and optical band gap can hardly be changed by argon pressure.The values of Tav were over 80%,and Eg were all above 3.342 e V which is more than that of none-doped Zn O thin films.(4)Process parameters can affect the electrical property of thin films.The four-point probe measurement results show that the electrical resistivity of GZO:Ti thin film is of the orde of 10-3 ?·cm,and the figure of merit ? is from 1649.7 ?-1·cm-1 to 4068.9 ?-1·cm-1.It is clearly that doping with Ti and Ga can change electrical resistivity and improve the electrical property of the deposited thin films.(5)The refractive index(n)and extinction coefficient(k)of GZO:Ti thin films were calculated by the method of the method of optical spectrum fitting.The result shows that both n and k decrease with the increment of wavelength,and the deposited thin films possess the normal dispersion characteristics in the visible region.The refractive index dispersion curve of thin films obeys the Wemple-Di Domenico single-oscillator model.(6)The optimum conditions for GZO:Ti thin films are obtained and shown as follows: target-substrate distance,75 mm;deposition temperature,610 K;argon rate of flow,25 sccm;argon pressure,0.5 Pa;sputtering power,180 W;and sputtering time,30 min. |
PDF Full Text Request