Preparation Of Al-Doped ZnO Films By Sol-Gel Method And Study Of Their Properties

Transparent conductive oxide thin films exhibit low resistivity and high transmittance in the visible light range. It was widely applied to various devices including solar cell, liquid crystal display as transparent and conductive oxide electrodes. Transparent conductive oxide thin films mainly include SnO₂, In₂O₃, ZnO and their doped system. ZnO thin films have recently gained much attention due to their good piezoelectric, photoelectric, gas sensitivity and stress sensitivity behaviors. The Al～(3+)-doped ZnO (AZO) thin films have become one of the focuses research because of its excellent optical and electrical properties.In this paper, the Al～(3+) doped ZnO thin films were deposited on glass substrates by sol-gel method. The crystal structure, transmittance and resistivity of thin films were mainly researched with different dopant concentration (1at%～12at%), annealing temperatures and atmospheres. The range of annealing temperatures were from 400℃to 600℃, and the annealing atmospheres were air, H₂ and Ar. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), spectrophotometer and four-point probe methods were employed to characterize and analyze the films.The results showed that AZO thin films prepared by sol-gel method have polycrystalline hexagonal wurtzite structure. The thin films annealed at 500℃in the air have the strongest preferred orientation. The conductivity of the films can be improved with different dopant concentration (1at%～12at%). And the minimum resistivity is obtained with dopant concentration 2at%.The annealing temperatures and atmospheres affect the resistivity significantly. In the air, the minimum resistivity of 5.18×10^-1Ω·cm is obtained at 500℃as the film doped with 2at%. After annealing in different atmospheres at 500℃, the films annealing in H₂ have minimum resistivity of 2.238×10^-1Ω·cm. Annealing temperatures and atmospheres have little influence on the transmittance of AZO thins films. Average optical transmittance of AZO thin films is from 85% to 90% in the visible light region.