Aluminum Doped Zno Thin Films By Sol - Gel Preparation And Performance

Transparent conductive oxide thin films exhibit low resistivity and high transmittance in the visible light range. Hence, they are widely applied to various devices including solar cell, defend screen of electromagnetism, liquid crystal displayer as transparent and conductive oxide electrodes. Among them, zinc oxide (ZnO) film has been attracting more and more attentions because of its piezoelectric, optoelectric and pressure-sensitive properties.Up to now, there are many techniques used to the deposition of ZnO thin films, such as magnetron sputtering, chemical vapor deposition (CVD), vacuum evaporation, sol-gel technique and so on. By comparsion, the sol-gel technique is easy for doping and the dopant can be accurately controlled. Moreover, it has great potential for the preparation of large area films as well as complicated forms on various substrates.In this thesis, Al-doped ZnO (AZO or ZAO) thin films were prepared on glass slides by sol-gel process at room temperature plus heat post-treatment. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to analyze the composition, structure and morphology of the films. Ultraviolet-visible spectrophotometry was applied to measure the transmittance properties of the films.Results show that the obtained films possess of hexagonal wurtzite structure with highly preferred orientation along the (002) plane (or C axis). Al3+ doping into ZnO films was not found to affect the basic ZnO crystal form of the films. Al3+ substitutes the Zn's place in ZnO lattice, i.e. substitute doping. After heat treatment, Al3+ doped ZnO grains show hexagonal needle-shaped (or pillar-shaped) crystal morphology. The higher the heat treatment temperature is, the better the transmittance of the films is. For the film after 600℃heat treatment, the transmittance of the film increases first and decreases afterwards with the increase of Al3+ doping concentration, the best transmittance presents at 2%of Al3+ doping concentration. The effect of the lattice deformation arising from the dopants, which leads to the decrease of the transmittance of the film, could not be ignored at higher Al3+ doping concentration anymore.