Study On Preparation And Properties Of AZO Thin Films By Sol-Gel Method

Al-doped ZnO (AZO) thin film is a new kind of wide band gap semiconductor material, which can be widely used in preparing transparent electrode and transparent window materials because of its transparent and conductive properties. The UV emission properties can be used in UV detectors and laser. AZO thin films were prepared by magnetron sputtering, chemical vapor deposition, sol-gel method and so on. At present, the most important things for researchers in making the AZO thin film is the stability, reproducibility and uniformity in a large area. In this paper, AZO thin films of high transparency, low resistivity, high photoluminescence properties have been prepared by sol-gel method.In this thesis, the author choose zinc acetate dihydrate as zinc source, aluminum chloride hexahydrate as the aluminum source, ethylene glycol monomethyl ether as an organic solvent, monoethanolamine as stabilizer. The sol was prepared according to a certain ratio, and through spin coating and annealing process, the AZO thin films with excellent optical and electrical properties were prepared. The influence on the morphology, optical properties and electrical properties of AZO thin films were researched, setting the influence factor as different substrates, different annealing temperatures, different intermingled quantity, gradient doping and buffer layer.The experiment results showed that the silicon substrate was more favorable than the glass substrate in preparing oriented along the c-axis plane of AZO thin films and had lower resistivity on silicon substrate. When alumina doping content of 1.0at%, the annealing temperature was 600℃, the annealing time was 180min, the AZO thin film with the most excellence photoluminescence properties and low resistivity can be prepared, the lowest resistivity of the thin film was 4.64×10-3Ω·cm. The sharp intrinsic emission peak and near the UV emission peak indicated that the film had excellent photoluminescence properties. The annealing temperature and doping concentration didn't affect the transmittance of AZO thin films, which mainly affected by film thickness. With the increase of aluminum doped concentration, the surface roughness of AZO thin films became poor, the electrical conductivity decreased, the intrinsic luminescence peak intensity decreased and the visible emission peak intensity increased significantly. Compared to non-gradient doping, AZO thin films by gradient doped possess more stable and low resistivity in a wider annealing temperature area, as well as higher intrinsic PL peak intensity. MgO buffer layer's adding made the preparation of AZO thin films with excellent optical and electrical properties more easily and more stable. The band gap of AZO thin films is 3.2eV in room temperature, the aluminum doped increased the band gap of AZO thin films significantly. With the annealing temperature increased, the band gap decreased, with the increase of aluminum doped concentration, the film's band gap increased gradually.