Study On The Preparation Of Al-and Si-doped ZnO Films And Their Properties

Aluminum doped zinc oxide (ZAO) transparent conductive thin films with high transparency in visible wavelength range, high infrared reflection, and low resistivity will be widely used in many fields such as flat display panel, thin film solar cell, and heat reflection glass.In the work, ZAO ceramic targets were manufactured by a composite process of cold mould pressing and sintering. ZAO thin films were prepared by middle-frequency magnetron sputtering with the ZAO target. The effects of Al₂O₃ concentration in target on the electrical and optical properties of ZAO films were investigated. The results showed that ZAO film with optimum properties can be obtained by sputtering the ZAO ceramic target with Al₂O₃ concentration of 2.0wt%.Four-point probe tester was employed to measure electrical properties. UV-VIS and IR spectrometry were used to examine optical properties at different wavelength. Surface morphology and microstructure were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD), respectively.The effects of the technological parameters for preparing ZAO film including base vacuum pressure, target current density, oxygen pressure, substrate temperature, and argon gas pressure on the properties of ZAO films were systematically studied. Based on a lot of experimental results and comprehensive analysis, the optimum technological parameters were determined as follows: substrate temperature: 250℃, target current density: 6.67 mA/cm², base vacuum pressure: 2.0×10^-3 Pa,argon gas pressure:0.8 Pa without oxygen. Under the optimum preparation condition, the ZAO film with the best properties of average transmittance of 86% in visible range, sheet resistance of 32Ω/â–¡, and resistivity of 4.6×10^-4Ω·cm at film thickness of 127 nm, which reach international level, was obtained.The optical properties and surface morphology characterization of milky ZAO films were studied. The technological parameters for preparing milky ZAO films with various hazes and surface roughnesses were obtained by analyzing the effects of argon gas pressure, substrate temperature, and film thickness on the surface structure of milky films. Meanwhile milky ZAO films with similar haze to milky FTO films, which was already used commercially, can be easily deposited.The influence of film thickness, substrate temperature, and argon gas pressure on the performance of infrared reflection was experimentally analyzed. The deposition parameters for the ZAO films with high infrared reflection of exceeding 80% were gotten.Dense Si-doped ZnO (ZSO) ceramic target could be also prepared by cold mould pressing plus sintering under optimized technological parameters. The influence of substrate temperature and argon gas pressure on the electrical and optical properties of ZSO films was preliminary investigated.