Properties Of Al-doped ZnO Thin Films Prepared By Pulsed Laser Deposition

Transparent conductive oxides (TCOs) have been extensively used in optoelectronic device because of their high visible transmittance, low DC resistivity, high infrared reflectance and absorbance in the microwave region. Almost all TCO films now being put to practical use are made of indium tin oxide (ITO), a compound likely to become unavailable due to the growing scarcity of its component metal indium. To cope with the depletion of indium, a strong interest has recently turned to TCO films based on a zinc oxide system. Compared with indium tin oxide (ITO), ZnO films have many advantages such as have high transmittance in the visible region, low resistivity, cheap and abundant raw material, nontoxic nature, easyfabrication and high stability in hydrogen plasma Aluminum oxide doped zinc oxide(AZO) thin films have been prepared by thermal evaporation, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sol-gel, spray pyrolysis and magnetron sputtering, and pulsed laser deposition (PLD). Pulsed laser deposition has advantages in target fabrication and keeping the composition of films with the target.A comprehensive report of our results on fabrication of AZO films with different deposition conditions, and their effects on the structural, electrical and optical properties of the AZO films are given in this paper.The experimental results show that the XRD spectra are dominated by the (002) reflection for all films confirming the strong (002) textures. The electrical resistivity of films deposited between 240℃~310℃ shows lowest resistivity; the electrical resistivity of films deposited at low oxygen pressure shows low resistivity; the electrical resistivity of films deposited at high laser energy shows low resistivity the electrical resistivity of films deposited at high pulsed laser repeat shows low . resistivity; the electrical resistivity of films can be further reduced by post-deposition annealing at high temperature in argon. The average transmission of AZO films in the visible range is 90%.The conduction electrons in these are supplied from donor sites associated withoxygen vacancies, Zn interstitial ions, Al ions on substitutional sites of Zn ions andAl interstitial atoms. The mobility is mainly dominated by ionized impurity scattering and grain boundary scattering. The optical direct band gap of films was dependent on the carrier concentration, which can be attributed to the Burstein-Moss effect.