| Transparent conductive films are a kind of functional thin film material widely used in photoelectronic devices such as solar cells, liquid crystal display, energy-saving glass, etc. Among the different materials within this category, impurity-doped zinc oxide (ZnO) shows high visible transmittance combined with metal-like conductivity and is a promising alternative to indium tin oxide (ITO) due to its abundance in nature, low cost, relatively low deposition temperature, and stability in hydrogen plasma compared to ITO.Al-doped ZnO (AZO) transparent conductive thin films were grown by DC reactive magnetron sputtering at room temperature in our work. The influences of deposition pressure and oxygen partial pressure on the film properties were studied. To further improve the electrical property, Cu-based AZO multilayer films were prepared and the effects of Cu layer processing parameters on the multilayer film properties were systematically investigated. The main results are obtained as follows:1. High quality AZO thin films were prepared on glass substrates by DC reactive magnetron sputtering from a Zn-Al alloy target at room temperature. It's critical to optimize the oxygen partial pressure while other key factors such as Al content (4 at.%), growth temperature (about 25℃), deposition pressure (0.7 Pa), etc. are fixed. AZO thin films grown with oxygen partial pressure in the range from 0.027 Pa to 0.052 Pa are of acceptable performance, such as preferred c-axis orientation, smooth surface with grains uniformly stacked up and entirely compact, low resistivity in the 10-3Ωcm order, and high visible transmittance above 90%. The lowest resistivity of 4.11×10-3Ωcm and the optimized figure of merit (φTC) of 2.38×10-3Ω-1 are obtained under oxygen partial pressure of 0.027 Pa.2. AZO/Cu bi-layer, Cu/AZO bi-layer. and AZO/Cu/AZO tri-layer films were prepared on glass substrates by DC magnetron sputtering. The influences of Cu layer thickness, AZO layer thickness, and growth temperature on the multilayer film properties were studied. The Cu layer thickness shows great influence on the photoelectrical properties. With an ultrathin Cu layer introduced, the conductivity of the multilayer films improves remarkably, while the visible transmittance slightly decreases. The AZO layer thickness has minor influence on the electrical properties. while it modulates the position of transmission peak. AZO/Cu bi-layer films possess superior photoelectric properties over the other two, with low resistance of 21.7Ω/sq and acceptable transmittance of 80% simultaneously obtained, and correspondingφTC is 4.82×10-3Ω-1. Moderate heating is favorable for the over-all performance improvement of the AZO/Cu and AZO/Cu/AZO multilayer films. AZO/Cu bi-layer films prepared at 150℃show optimizedφTC of 1.11x10-2Ω-1 and high near-infrared reflectivity above 70% in a wide wavelength range.3. AZO/Cu bi-layer, Cu/AZO bi-layer, and AZO/Cu/AZO tri-layer films were prepared on PC flexible substrates aiming at their application in flexible devices. The effects of Cu layer deposition time and sputtering power on the multilayer film properties were investigated. Under same conditions, AZO/Cu bi-layer films have the highest visible transmittance, while AZO/Cu/AZO tri-layer films have the highest conductivity combined with the best near-infrared reflection property, and Cu/AZO bi-layer films show the poorest performance. The largestφTC of 3.47×10-3Ω-1 for AZO/Cu and 2.48×10-3Ω-1 for AZO/Cu/AZO can be obtained under optimizated conditions.
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