Pulsed laser deposition of polycrystalline zirconia thin films
Introduction
The stabilized and partially stabilized zirconia have been intensively studied for their interesting mechanical, electrochemical and optical properties. Stabilized zirconia is used in gas sensors, solid oxide fuel cells, corrosion or heat resistant mechanical parts. The preparation of these materials in thin layers would allow to extend their applications to optical or electrochemical devices. Thin films of zirconia have been deposited by various methods like MOCVD [1], RF sputtering 2, 3, or pulsed laser deposition (PLD) [4]. In this work, we study the influences of the target composition and structure on the crystallization and optical properties of the laser deposited films and also the influence of the temperature of the substrate during the deposition process.
Section snippets
Experimental
Thin films were deposited by laser ablation of zirconia ceramic targets which were prepared by sintering stabilized zirconia powders (Tosoh TZ-3Y for Y-doped zirconia and Goldschmidt for Ca- and Mg-doped zirconia). Four different types of targets were prepared and characterized by X-ray diffraction (see Table 1).
The targets were fastened to a rotating holder (2.5 rpm) in a vacuum chamber which was evacuated to a base pressure of 5×10−7 mbar. They were then irradiated under flowing oxygen (at a
Results and discussion
The low angle X-ray diffraction patterns of the thin films were compared to the (normal incidence) diffraction patterns of the ablated target and the phase identification was made according to the JCPDS files [5]. Whatever the type of target used for ablation and the temperature of the substrate, the phase structure of the deposited films is shown to be identical to those of the initial target material (Fig. 1Fig. 2). When the target is either tetragonal or cubic, the resulting film is either
Conclusion
Excimer laser ablation of stabilized or partially stabilized zirconia is shown to allow production of crystallized and transparent zirconia thin films on fused quartz at moderate substrate temperature (∼500°C) and oxygen pressure (0.3 mbar) and without any further annealing. This one-step method allows also to reproduce the stoichiometry of the initial target together with its crystalline phase. In the pressure and temperature conditions which are described in this work, the monoclinic phase
Acknowledgements
This work is supported by DGTRE, Ministère de la Région Wallonne, Belgium.
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