Study Of The Preparation And Properties Of ZnO: Al Thin Films Prepared By Sol-gel Technique

Transparent conductive oxide thin films exhibit outstanding optical and electrical properties,such as low resistivity and high transmittance in the visible range.This is because these films have high carrier concentration and wide optical band gap.The transparent conductive oxide thin films include chiefly SnO₂,In₂O₃,ZnO and their dopant systems.Recently,the study of ZnO thin films have become one of the research focus nationally and worldly.Al-doped ZnO(AZO)thin films are emerging as an alternative potential candidate for ITO(Sn-doped In₂O₃) flims not only because of their comparable optical and electrical properties to ITO films,but also because of their higher thermal and chemical stability than ITO films when expose to hydrogen plasma.In our experimentals,zinc acetate dihydrate is used as starting material; 2-methoxyethanol and monoethanolamine(MEA) are used as solvent and stabilizer, respectively;the dopant source of aluminum is aluminum chloride hexahydrate.The AZO thin films are prepared on glass substrate(microscope slides) by Sol-Gel spin-coating process.The influence of the process conditions on the surface morphological,structural, electrical and optical properties of AZO films are investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),four-point probe method and UV-VIS spectrophotometer,respectively.The results prove that the films are polycrystalline with a structure of preferred orientation of c-axis ZnO hexagonal wurtzite type.The sol concentration,dopant concentration,drying temperature,heat treatment temperature,cooling condition,and the thickness of the coating all influence the structural,electrical and optical properties of the AZO thin films in various degree.The optimum technological parameters for the best optical and electrical properties of AZO thin films are that the sol concentration is 0.5mol/l,the dopant concentration is 0.5 at.%,the drying temperature is 300℃,the heat treatment temperature is 550℃,the duration of heat treatment is 1 h,and the film is cooled at -15℃.