Study Of The Preparation Of Transparent And Conductive AZO Thin Films By Sol-gel Technique

Transparent conductive oxide thin films exhibit outstanding optical and electrical properties, such as low resistivety and high transmittance in the visible range etc, because of high carrier concentration and wide optical band gap. At present transparent conductive oxide thin films include chiefly SnO2, In2O3 ,ZnO and their dopant system. Recently, ZnO thin films have become one of the focuses of research nationally and worldly, and emerged as the best alternative candidate for In2O3 thin films. Transparent conductive oxide thin films doped with suitable dopants have more excellent optical and electrical properties, and are applied widely to various electrical and optical devices including liquid crystal display, solar cell, hot mirror and surface acoustic wave devices as transparent and conductive oxide electrodes.In this paper, the Al3+-doped ZnO thin films were deposited on substrates by sol-gel method from 2-methoxyethanol solutions prepared by Zinc acetate as precursor, DEA as stabilizer. Homogenous transparent ZnO thin films doped with Al3+ were formed finally by diping, drying, pre-heattreatment and annealing.Optimum study of technological parameters for the preparation of AZO thin films by sol-gel was carried through L9 (34) orthogonal design. The optimum technological parameters for the best optical and electrical properties of AZO thin films were that the sol concentration was 1mol/L, the dopant concentration was 3at. %,the annealing temperature was 600℃, and the number of coatings was 16.The structural , optical and electrical properties of AZO thin films were studied by a scanning electron microscope(SEM), a UV-V IS-NIR spectrophotometer and a four-point probe method. The result showed that the sol concentration, the dopant concentration,the annealing temperature,the number of coatings had influence in various degree on the photoelectric performance of the AZO thin films. Increasing the dopant concentration and the annealing temperature could reduce resistivity of thin films, but too many dopant concentration and too high annealing temperature would increase the resistivity of thin films instead; Increasing the density of the sol and the numberof coatings could increase the thickness of thin films, the increase of the thickness of the thin films would cause the reducing of the resistivity of the thin films.Increasing the dopant concentration and the annealing temperature had not influenced the average transmission rate within the range of visible light of the thin films basically, but could promote the absorption of the films to move bluely; Increasing the density of the sol and the number of coatings could reduce the transmission rate within the range of visible light of the films. There was porous structure within the thin films, the crystalline grains were even in size, and the form of the grains became almost round.