Effects of Processing Parameters on KrF Excimer Laser Ablation Deposited ZrO 2 Films
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EFFECTS OF PROCESSING PARAMETERS ON KrF EXCIMER LASER ABLATION DEPOSITED ZrO2 FILMS GARY A. SMITH*, LI-CHYONG CHEN**, AND MEI-CHEN CHUANG*** *Evans Central, Minnetonka, MN 55345 **GE Corporate Research and Development, Schenectady, NY 12301 ***IBM East Fishkill Facility, Hopewell Junction, NY 12533 ABSTRACT Systematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and 02 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the 02 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing 02 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed. INTRODUCTION Laser ablation deposition (LAD) is rapidly emerging as the technique of choice for producing high quality, high temperature superconducting (HTcS) thin films. Specific advantages of LAD include greater ambient atmosphere and composition control and lower substrate temperature than competing techniques. In addition to the HTcS application, a rather wide application of the LAD technique has been reported in the literature over the past few decades [1]. However, the tremendous potential use of LAD as a simple and versatile method for thin film preparation has largely not been realized yet. ZrO2 and yttria containing ZrO2 are of great technological importance, and the requirements of the macro and micro-structure depend on the specific use of the materials. For example, dense, transparent, and stress-free films with higher crystallinity are desirable in optical applications [2], whereas an open columnar structure, which exhibits greater strain tolerance, is beneficial for the thermal barrier coatings in high temperature applications [3]. In this work, we explored the flexibility of fabricating yttria containing zirconia with different deposition characteristics using the LAD technique. The deposition rate as well as the microstructure a
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