Study On Properties Of ZAO Targets And Transparent Conductive Films

Recently, Due to low cost, non-toxicity, and high stability in H2plasma atmosphere with good electrical and optical properties, transparent conductive oxide film, Al doped ZnO (ZAO) has attracted much attention, become a hot issue of transparent conductive thin films field and preferred materials instead of ITO films.In this paper, ZnO powder and Al(NO3)39H2O as the main raw materials fabricated ZAO ceramic targets which prepare transparent conductive films by sintering in atmospheric pressure. ZAO films were prepared by DC magnetron sputtering in pure argon gas atmosphere using ZAO ceramic target. Physical properties and micrographs of ZAO ceramic targets were investigated in different Al doping and sintering temperature. The effects of deposition temperature and deposition current to the thin film performance was studied. The main results were obtained as follows:Firstly, with increasing of the Al doping concentration, the resistivity of the ZAO target increases first, then decreases. The lowest resistivity was obtained at atom ratio of Al to Zn is3:97. The density of the target increase with the sintering temperature increase. When the sintering temperature exceeded1300℃, Al integrated Zn and O atom and generated ZnAl2O4that leaded to increasing resistivity of ZAO ceramic target. With the sintering temperature increase, the ZnAl2O4increase. When the proportion of Al:Zn atom was3:97, the sintering temperature was1400℃,the resistivity of ZAO target was the lowest,2.5×102Ω·cm.Secondly, with increasing of the substrate temperature, the resistivity of the ZAO thin film decreases first, then increases. the transmittance of the visible increases first, then decreases. Calculated by the XRD spectrum of ZAO thin film, the compressive stress was found in the ZAO thin film, is released with the increasing substrate temperature. When the substrate temperature is300℃, the sputtering current is200mA and the sputtering pressure is0.6Pa, the resistivity of ZAO thin film is1.7×10-3Ω·cm, the transmittance is90%, the band gap is3.67eV, the Urbach energy is0.312eV, the electronic dispersion is7.869eV, have the most stable refractive index.Thirdly, the ZAO thin films were prepared on flexible substrate in low temperature. Sputtering current is an important factor affecting the film properties. The experiments have shown that the increasing of the sputtering current make the film resistivity decrease. When the sputtering current is120mA, the lowest electrical resistivity of the ZAO thin film on PMMA substrate is found to be about5.7×10-2Ω·cm, on the PC substrate is found to be about4.75×10-2Ω·cm. When the sputtering current exceeds120mA, the flexible substrate temperature rises to97℃, the flexible substrate easy to deformation. The average transmittance for all ZAO thin films on flexible substrates is over77.5%in the visible range.