AVS 50th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeP

Paper TF-WeP17
Low-Resistivity Polycrystalline ZnO:Al Thin Films Prepared by Pulsed Laser Deposition

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: H. Tanaka, Kanazawa Institute of Technology, Japan
Authors: T. Minami, Kanazawa Institute of Technology, Japan
H. Tanaka, Kanazawa Institute of Technology, Japan
K. Ihara, Kanazawa Institute of Technology, Japan
T. Miyata, Kanazawa Institute of Technology, Japan
Correspondent: Click to Email
Recently, a very low-resistivity Al-doped ZnO (ZnO:Al, AZO) films comparable to ITO films were attained on glass substrates by pulsed laser deposition (PLD) method. In this report, we describe the preparation of low resistivity AZO thin films, including a description of conditions necessary to obtain the low resistivity on the order of 1×10@super -4@@ohm@cm. The AZO films were deposited on glass substrates by PLD using an ArF excimer laser. The deposition was carried out under the following conditions: pressure, 10@super -4@ Pa; substrate temperature, 180-350@super o@C; target-substrate distance, 50 mm; substrate, OA-2 glass; and target, sintered ZnO+Al@sub 2@O@sub 3@(1-3 wt.%). All AZO thin films prepared with a thickness of 200 to 700 nm exhibited an average transmittance above 85% in the visible range. In order to obtain low-resistivity AZO films, it was necessary to optimize the relationship between the target sintering conditions and the deposition conditions. The obtained resistivity decreased as the substrate temperature was increased, reached a minimum at a temperature of about 240@super o@C, and then increased with further increases of the temperature. The decrease of resistivity associated with the increase of temperature to about 240@super o@C resulted from an increase of Hall mobility, whereas the increase of resistivity with higher temperatures resulted from a decrease of carrier concentration. The Hall mobility increase was found to be correlated to an increase of crystallite size, as evaluated from the (0002) x-ray diffraction peak. On the other hand, the Al content in the films increased gradually as the substrate temperature was increased. The decrease of carrier concentration was ascribed to an increase of oxygen content in the films. As another example, the resistivity decreased as the film thickness was increased. As above, the resistivity decrease was also correlated to a Hall mobility increase resulting from an increase of crystallite size. It is concluded that differences in obtainable Hall mobility can be attributed to differences in the crystallinity such as crystallite size.