Investigation Of Zinc Oxide Based Transparent Conductive Films Prepared By Dual-target Reactive Magnetron Sputtering

As the alternative of indium tin oxide (ITO) transparent conductive film,Aluminum-doped zinc oxide (AZO) film has drawn more and more attentions due toits excellent optivoltaic performance and the other characteristics such as abundantresource, low cost and non-toxic. It can be widely used in flat-panel display,thin-film solar cells, touch screen and other optoelectronic devices. Therefore,lowering its cost and improving the AZO’s performance have great significances onreducing optoelectronic devices’ cost. Magnetron sputtering method has theadvantages of high deposition rate, low substrate temperature and good filmadhesion. It is widely used to prepare AZO thin films.In this paper, AZO thin films were prepared by reactive magnetronco-sputtering method, using zinc and aluminum double targets and were thenannealed to improve its overall performance. Besides, in order to overcome thepuzzle of poor photovoltaic performance of AZO film deposited at roomtemperature, AZO/Al/AZO and ZnO/Ag/ZnO films with sandwich structure werealso prepared by inserting an Al layer and a Ag layer, respectively.The sputtering experimental result of AZO films indicate that the crystallizationquality of films are determined by sputtering power, sputtering pressure and oxygento argon flow ratio. AZO films with different Al doping amount are obtained byincreasing Al target radio-frequency power when Zn target power is kept constant.The effects of Al doping content on the structure and performance of AZO filmwas studied. The samples were annealed at500℃in the mixing atmosphere of N2and H2for1.5hours. The experimental results indicate that it can be obtained for thelowest electrical resistivity of3.95×10-3Ω·cm and the average transmittance invisible spectral region of83.68%when Al doping content is1.34at.%.The sputtering experimental results of AZO/Al/AZO and ZnO/Ag/ZnO withsandwich structure indicate that the electrical resistivity is decreased at first andthen maintains a constant with increasing the thickness of middle layer, while thetransmittance is decreased. The transmittance increases with the increasing ofthickness of the outer layers and the transmittance increases at first and then keepstable. It can be obtained the electrical resistivity of7.06×10-4Ω cm and thetransmittance of65.76%when AZO/Al/AZO film is of thickness of65/15/65nm;and the electrical resistivity of5.66×10-5Ω cm and transmittance of71.17%whenZnO/Ag/ZnO film is of50/15/50nm. The figure of merits is3.15×10-4Ω-1and6.80×10-3Ω-1, respectively. It is thus obvious that the electrical properties of AZO films can be strongly improved by introducing intermediate metal layer, and theoptoelectronic performance of the sandwich-structure films with the middle Aglayer is better than the middle of Al layer.