Characterization Of Yttrium And Indium Co-doped Zinc Oxide Thin Films

ZnO osxide is a direct band gap n-type semiconductor with an energy gap of?3.37eV.It has great potential applications in optoelectronic devices.But its performance is not stable when the temperature is over 15 0 ?.We hoped that co-dopig can enhance the performance of ZnO based TCO films.In exists in the lattice in the form of substitution because the electronegativity of In is large.Besides the lattice changes caused by incorporation of In are little.Incorporated the rare earth metal yttrium(Y)into ZnO substrate can widen the material bandgap,improve the light transmittance,decrease the resistivity and enhance the ultraviolet radiation of the film material.YIZO transparent conductive film can be prepared at room temprature and the process is simple.If we find the best conditions for film preparation and optimize the properties of the YIZO films,their applications will to be a great significance in the field of photovoltaic device.1.YIZO transparent conductive filmsIn this paper,Y-In co-doped ZnO thin films were deposited on glass substrates by RF magnetron sputtering,with different sputtering power,different sputtering time and different oxygen partial pressure.The structural,electrical and optical properties of YIZO thin films are investigated in detail.The main contents and conclusions are as follows:(1)The effects of sputtering power on the properties of YIZO thin films:The power on the YIZO target varied from 80,100,120 to 140W.Through the testing and data analysis on XRD,AFM,UV-visible spectrophotometry and Hall-effect of YZO thin films,we found out that,all films are amorphous structure.The average transmittance in visible range is over 84%and the band gap of YIZO films decrease from 3.42eV to 3.15eV with the increase of sputtering power.The mobility increases and when the sputtering power is 120 W,the carrier concentration is the highest and the resistivity is the lowest(6.48X×10-2?·cm).(2)The effects of sputtering time on the properties of YIZO thin films:The sputtering time varied from 30,40,50 to 60 minutes.Through the testing and data analysis on XRD,AFM,UV-visible spectrophotometry and Hall-effect of YZO thin films,we found out that,all films are amorphous structure.The average transmittance in visible range is over 84%and the band gap of YIZO films decrease from 3.19eV to 3.02eVwiththe increase of sputtering time.The carrier concentration decreases while the mobility slightly increases with increasing sputtering time.When the sputtering power is 30min,the resistivity is the lowest(1.5O×10-?·cm).(3)The effects of sputtering pressure on the properties of YIZO thin films:Sputtering pressure was set as 0.4Pa?0.7Pa?1.0Pa and 1.3Pa.Through the testing and data analysis on XRD,AFM,UV-visible spectrophotometry and Hall-effect of YZO thin films,we found out that,all films are amorphous structure.The average transmittance in visible range is over 84%.When the sputtering pressure is 0.7Pa,the band gaf YIZO film is the highest(3.31 eV).(4)The effects of oxygen partial pressure on the properties of YIZO thin films:the oxygen partial pressure(Po2)was changed from 0,0.1,0.2,0.3 Pa.Through the testing and data analysis on XRD,AFM and UV-visible spectrophotometry,we found out that all the films are amorphous.The average transmittance of these films in the visible wavelength is over 84%and increases with increasing oxygen partial pressure.2.YIZO thin film transistorsWe used the P-type silicon as the gate electrode,YIZO thin film as active layer and the aluminum medal as source and drain electrodes to prepare the YIZO thin film transistor(YIZO TFT).Through the tests,we found out that the YIZO TFT was n-channel depletion mode device.When the sputtering time was 2 min,the performance of YIZO TFT is better.The subthreshold swing is 1.12 V/dec.,the threshold voltage is-0.94V,the filed effectmobility is 0.53cm2/V·s and the Ion/Ioff is 3.65 X 104.