High-throughput Studies on Photochemical Properties of Transition Metal-Doped SrTiO 3 Epitaxial Thin Films
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High-throughput Studies on Photochemical Properties of Transition Metal-Doped SrTiO3 Epitaxial Thin Films T. Ohsawa1, H. Koinuma2, 3, 4 and Y. Matsumoto1, 2 1
2
Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan CREST-Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
3
4
Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581, Japan National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0044, Japan
ABSTRACT Combinatorial pulsed laser deposition approach is suitable to study complex effects such as composition, thickness and
surface structure on thin film-based photocatalysis in
high-throughput manner. We fabricated composition spreads and thickness gradient films of transition metal-doped SrTiO3(001) on various oxide single crystal substrates and evaluated their photocatalytic activity by the use of photoreduction of Ag+ in AgNO3 solution. We found anomalous film thickness and substrate effects on the Ag-photodeposition in the V-doped SrTiO3 epitaxial thin films grown on the Nb:SrTiO3(001) substrate.
INTRODUCTION Nano-scale understanding of photocatalysis depending on surface compositions and structures has been an important issue not only for basic science, but also for practical use. The accurately engineered oxide surface and interface play a significant role in appearance of the novel photocatalysis because it is governed by a lot of factors such as crystal orientation, surface morphology, impurities and defects. Consequently, it becomes difficult to elucidate elemental photocatalytic properties in polycrystalline form. An epitaxial oxide thin film whose composition and structure are atomically designed would thus be a good model photocatalyst to elucidate the elemental properties and it becomes more effective by combining with combinatorial solid-state technology. Combinatorial laser molecular-beam epitaxy (laser MBE) enables us to fabricate well-defined thin films epitaxially grown on a single crystal substrate [1, 2], thereby to investigate their more intrinsic photocatalytic properties. In this paper, we report on the
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development of a high-throughput experimentation of photocatalyst research, together with new findings such as anomalous film thickness and substrate effects on the photocatalysis in the thin film library based on SrTiO3.
EXPERIMENTAL DETAILS Epitaxial thin films were grown by combinatorial laser MBE method. During the growth, a novel slide mask was used for efficient fabrication of binary- and ternary composition spreads on one substrate [3]. The mask motion was automatically controlled so as to deposit less than one ML film in one deposition period, synchronized with target switching. Figure. 1 illustrates a high-throughput experimentation of photocatalyst in this study. First, thin films were pulsed laser-deposited by KrF excimer laser with repetition rate of 5Hz and laser fluenc
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