Preparation And Properties Study Of Ag Based Multilayer Transparent Conductive Films

The traditional transparent conductive material tin doped indium oxide (ITO) is widely used as transparent electrodes in various kinds of displays and solar cells as its low sheet resistance and high visible transmittance. Since the scarce resource In is not only expensive but also toxic, so reducing or avoiding the consumption of In becomes the development trend of transparent conductive film. As a result, fluorine doped tin oxide (FTO) and aluminum doped zinc oxide (AZO) which are substitutes for ITO have attracted more and more attention. However, due to the restriction of conductive mechanism of the semiconductor, transparent conductive oxide ITO, FTO and AZO cannot meet the higher requirements in conductive properties of photoelectric device, further explorations to the preparation and properties of ITO/Ag/ITO (IAI), FTO/Ag/FTO (FAF) and AZO/Ag/AZO (ZAZ) are necessary.In this work, ITO film, Ag film, ITO/Ag films, Ag/ITO films, IAI films, FTO film, FAF films, AZO film, AZO/Ag films and ZAZ films were fabricated using the direct current (DC) magnetron sputtering on glass substrate at room temperature.The techniques such as scanning electron microscope, atomic force microscopy, surface contourgraph, visible spectrophotometer and four-point probe were used to represent the surface morphology, film thickness, optical and electrical properties of films.The surface morphology, deposition rule and photoelectric properties of ITO film and Ag film were analyzed. The result shows that the deposition of ITO film increases the surface roughness of glass. With deposition time of ITO increasing, deposition rate of ITO film increases, but transmittance and square resistance of ITO film decreases gradually. With deposition time of Ag increasing, deposition rate, transmittance and square resistance of Ag layer decrease as island Ag transforms to continuous film. The result of analyzing the structure and photoelectric properties of IAI shows that conductivity of IAI films depends on the Ag layer and is influenced by outer ITO layer. ITO(34nm)/Ag(llnm)/ITO(34nm) obtain the best properties that Tmax is 85.97%, Rs is 5.46Ω/sq and ΦTC is 0.0404Ω-1.The structure, deposition rule and photoelectric properties of FTO film were analyzed. The result shows that with deposition time of FTO increasing, deposition rate changes little and transmittance decreases as homogeneous FTO transforms to large cellular, but square resistance of FTO films are always beyond the measurement range. The research of FAF films shows that FTO(50nm)/Ag(llnm)/FTO(50nm) obtain the best properties that Tmax is 83.31%, RSis 7.19Ω/sq and ΦTC is 0.0224Ω-1. The comparison of FAF and IAI shows that the Huck Performance Indexes of FAF are lower than that of IAI which have better properties. When the thickness of Ag film is 11nm, Both IAI and FAF films obtain the best properties.The structure, deposition rule and photoelectric properties of AZO film were analyzed. With the deposition time of AZO increasing, AZO film maintains small cellular growth and the deposition rate keeps stable, but the transmittance and square resistance decease gradually. By comparison, we got the order of deposition rate from high to low is FTO, ITO and AZO, The order of optical properties from high to low is AZO, ITO and FTO. The order of electrical properties from high to low is ITO, AZO and FTO. AZO(25nm)/Ag films with different thickness of Ag layers were prepared and their surface morphology were analyzed. The result shows that the Ag on AZO film grows from island to network and finally forms continuous film. Furthermore, critical thickness of Ag film on AZO substrate is the same to that on glass substrate. The research of ZAZ films shows that AZO(27nm)/Ag(9nm)/AZO(27nm) obtain the best properties that Tmax is 86.28%, Rs is 4.29Ω/sq and ΦTC is 0.0533Ω-1. The comparsion of IAI, FAF and ZAZ shows that photoelectric properties of ZAZ films are obviously better than IAI films or FAF films and AZO/Ag(9nm)/AZO films obtain the best properties. The lower roughness of bottom AZO film and the lower deposition rate of outer AZO film lead to thinner Ag film continuous.