Low Temperature Preparation And Optimization Of AZO Transparent Conductive Films

Aluminum-doped zinc oxide thin film, a kind of transparent conductive oxide (TCO) thin film, is widely applied in various fields such as thin film photovoltaics, flat displays and LEDs. Meanwhile, the development of smart electronics hastens the research and development of flexible devices. Therefore, AZO thin films become a promising alternative to indium tin oxide (ITO) due to its abundance in nature, low cost and stability. According to reports, most AZO thin films are deposited under high temperature (200-400centigrade), which is not a proper condition for flexible substrate. Our study prepared AZO thin films under low temperature, and optimized the sputtering parameters such as substrate temperature and sputtering power. In order to further improve the conductivity of samples, our study prepared AZO/Ag/AZO multiple layers thin films, using dual targets sputtering. The effects of Ag thichness and AZO thickness on the comprehensive properties of multiple layers thin films were systematically investigated. The main results are obtained as follows:1. High quality AZO thin films were prepared on glass substrates by DC magnetron sputtering from an Al2O3:ZnO ceramic target at low temperature. When the sputtering parameters are fixed, the optimization of substrate temperature is crucial. The sample thin films show relative large grain sizes and small lattice when the substrate temperature are75～100centigrade. Meanwhile, the samples show low resistivity below10-3Ω·cm and high average transmittance above90%. The sample prepared under100centigrade shows a5.52×10-3/Ω figure of merit, which is better than those ITO thin films prepared at low temperature.2. Our study investigates the effect of sputtering power on the properties of AZO thin films, when the substrate temperatre is fixed at100centigrade. According to the results of AFM test, we broach a nucleation module under various sputtering powers. After investigation, our study founded that there exists a saturate nucleation density, which appears at280W. With the sputtering power exceeds280W, it will lead cluster phenomenon, which will then lead the surface roughness. However, the abundant sputtering particles under this situation will help repair defect in films and thus help improve the comprehensive propersties of samples. The best samples is prepared under360W sputtering power, shows a figure of merit of6.5×10-3/Ω.3. AZO/Ag/AZO multiple layer films were prepared on glass substrates by DC magnetron sputtering. The influences of Ag thickness and AZO thickness on the properties of multilayer film were studied. The Ag layer thickness shows great influence on the photoelectrical properties. With an ultrathin Ag layer introduced, the conductivity of the ultilayer films improves remarkably, while the visible transmittance decreases. The thickness of AZO layer has minor influence on the electrical properties. The optimum parameters are dAg=9nm, dAZO=40nm, under which condition the multiple layer film shows a figure of merit of3.55×10-2Ω-1. This kind of excellent TCO thin film has a bright future in application of transparent electrode.