Study On The Preparation And Optical And Electrical Properties Of Al-doped ZnO Thin Films

ZnO is a II-VI semiconductor material with wide band-gap, which has hexagonal wurtzite structure. ZnO thin films were widely applied in solar cell, UV detector, SAW device, gas sensor and transparent electrodes et al for their excellent properties. In recent years, Al-doped ZnO(AZO)thin films has become a hot issue of transparent conductive thin films field and preferred materials instead of ITO films not only because of their comparable optical and electrical properties (high optical transparency in the visible range, low electrical resistivity) to ITO films, but also because of their lower price and higher thermal and chemical stability under the exposure to hydrogen plasma than ITO.In this paper, High quality of AZO thin films were prepared by direct current (DC) reactive magnetron sputtering using a Zn target (99.99%) containing Al of 1.5%. The films obtained were characterized and analyzed by XRD, AFM, SEM, XPS and ultraviolet-visible and infrared light spectrophotometer.The conduction mechanism has been analyzed and the electrical properties had been investigated by Van der Pauw method. It was also found that Oxygen argon (O2/Ar) ratio and annealing temperature had great influence on the optical and electrical properties. The Seebeck and magnetoresistive effects were also studied.The experimental results showed that the AZO thin films had the structural, optical and electrical properties better. It was found that the obtained films were poly-crystalline and highly orientation growth with the C-axis perpendicular to the substrate surface. The crystallinity of AZO thin films became better after annealing treatment. The film stress decreased with increasing annealing temperature, while increases with increasing oxygen argon ratio. During the inspection by AFM and SEM, we found that the surfaces morphology of samples was even and smooth,The surface roughness was small.The films were composed of some excellent columnar crystallites. The XPS results were found that Zn existed only in the oxidized state and the concentration of Al was less and the presence of loosely bound oxygen on the surface of AZO thin films was reduced after Ar+ etching.Study for optical spectra of the films indicates that the average value of the optical transmittance of the films in the visible region exceeds 80%. With the annealing temperature increasing, the average optical transmittance increases and the absorption edge of the transmission curve of the films moves toward short wavelength. But with...