Al-doped Zno Thin Film Structure And Optical Properties

Al-doped ZnO (AZO) thin films have high conductivity and exhibit good optical transmittance in visible wavelength region(400-700nm). compared to Sn-doped indium oxide (ITO) films , AZO films have many properties, such as low cost, non-toxicity, high chemical stability under hydrogen plasma. Due to these unique properties, AZO films have wide applications, such as transparent conducting electrodes in solar cells, light emitting diodes and laser diodes. In this paper, a series of AZO films were prepared by using a KrF excimer laser at different deposited condition. Through the research of the structural and optical properties of AZO films, optimized conditions for growing AZO films were obtained. The results suggested that high quality AZO films with highly c-axis orientation could be prepared by PLD. By changing different deposited condition, some points have been obtained.(1)The AZO films were prepared at different substrate temperature. XRD results suggested that all samples have c-axis orientation as the substrate temperature changes from 100℃to 500℃.With substrate temperature increasing, the FWHM of ZnO (002) diffraction peaks become narrower. The crystallinity of the samples is improved. The AZO films grown at 400℃have the strongest (002) diffraction peaks and the best crystallinity. With further increasing of substrate temperature, The intensity of (002) diffraction peaks of the AZO films starts to become weak. When the substrate temperature is 600℃, we cann't find (002) diffraction peaks in the XRD spectra of the prepared AZO thin films. Therefore, higher substrate temperature damages the growth along c-axis orientation and crystallinity of AZO films. The surface morphology of the sample is strongly influenced by the substrate temperature. As the substrate temperature becomes higher, the crystal grains will more easily gather and extend around the islands which had been formed at earlier time, so the surface of the samples grown at higher substrate temperature forms the structure with longer and thicker islands. The transmittance of All of the samples grown through the changing of the substrate temperature in the visible wavelength region is above 75% and the transmittance of the AZO thin films grown at 400℃is the best.(2)The AZO films were prepared, at different oxygen partial pressure. The films grown among the oxygen pressure from 10mPa to 1Pa have good crystallinity. As the oxygen partial pressure increases further, the grains of the samples become small, the crystallinity degrades and the transmittance in the visible wavelength region decreases. The growth of AZO thin films along the c-axis is the best and the films prepared have the best crystallinity ,the biggest grains and the highest transmittance in the visible wavelength region when the oxygen partial pressure is 100mPa. The transmittance in the visible wavelength region of the AZO thin films depends on the quality of the crystallinity and the better the crystallinity of the films is ,the higher the transmittance in the visible wavelength region is.(3) Aluminum doped zinc oxide (AZO) thin films were prepared by sol-gel spin coating process on normal glass substrates. After every layer of thin film was coated, it was proceeded with heat treatment at certain temperature. This process was repeated seven times. Finally, Some films were annealed at 600℃in muffle furnace for two hours while the others were directly investigated without being annealed. The coatings have been characterized by X-ray diffraction and electrical resistance measurement. It was found that the structural and electrical properties of the prepared thin films were influenced by the temperature of the heat treatment and the treatment process that whether or not the thin films were annealed..