Nano-Creep Test for Anatase Polycrystalline Films

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NANO-CREEP TEST FOR ANATASE POLYCRYSTALLINE FILMS Hironori Sugata, Shigeo Ohshio, Hidetoshi Saitoh Department of Chemistry, Nagaoka University of Technology, Nagaoka, Niigata, 940-2188 JAPAN ABSTRACT We introduce an analytical technique for time-dependent deformation behavior of the polycrystalline films using a nano-indenter. This technique permits evaluation of structural deformation of the nanometer scale of the thin films. In this paper, good accuracy conditions were determined to measure deformation behavior of the polycrystalline films. The polycrystalline films of anatase were used to investigate the grain boundary structure. We prove that the analysis of time-dependent deformation behavior is effective to investigate the structure of the polycrystalline films. INTRODUCTION Recently an analytical technique for time-dependent deformation behavior has been proven to be an effective method to analyze microstructure of the amorphous films[1]. This method permits evaluation of structural deformation in the nanometer scale of the thin solid films. This technique may also detect the existence of the grain boundary of the polycrystalline films. A major problem exists when this technique applies to the structural analysis of the polycrystalline films. For example, Figure 1 shows a schematic diagram that illustrates the difference on the deformation between amorphous and polycrystalline films. Although homogeneous behavior is obtained on the amorphous material, heterogeneous behaviors are obtained on the polycrystalline films. The structures at the crystalline grain and the boundary are quite different. Therefore, the behaviors between them are observed as different data. The accuracy of this analytical technique may be affected by the difference in the creep behaviors between them. In order to apply this technique to the analysis of the polycrystalline films, we are required to understand the difference in creep behavior at every measurement point. In this study, time-dependent deformation behavior of the polycrystalline anatase films is introduced, and the grain boundary structure of the polycrystalline films are described and discussed. Samples were synthesized on the glass substrate using a chemical-vapor-deposition (CVD) technique operated under atmospheric pressure. Diamond tip

Diamond tip

amorphous

polycrystal

Figure 1. Schematic diagram that illustrates the difference on the deformation between amorphous and polycrystalline films. L4.7.1

EXPERIMENTAL DETAILS Polycrystalline anatase films were prepared by the CVD apparatus operated under atmospheric pressure with titanuimtetra-isopropoxide as the source complex, as described in detail elsewhere[2,3]. The reactant Ti(O-i-C3H7)4 was loaded in a vaporizer and vaporized at the temperatures of 140oC, 150oC and 160oC. The microstructure of the sample depends on the vaporizing temperature. The substrate was heated by an electric heater settled behind the substrate. The substrate temperature was held on 450oC. The reactant vapor was carried by nitrogen gas and spr