Anomaly of Thermal Properties in Thin Films of La 1-x Sr x CoO 3 Series Synthesized with a Combinatorial Processing
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Anomaly of Thermal Properties in Thin Films of La1-xSrxCoO3 Series Synthesized with a Combinatorial Processing Yoshiaki Takata1, Yutaka Adachi, Hajime Haneda1, Yoshiki Wada, Takefumi Mitsuhashi Advanced Materials Laboratory, National Institute for Materials Science, Namiki, Tsukuba, 305-0044, Japan. Makoto Ohtani Innovative and Engineered Materials, Tokyo Institute of Technology, Midori-ku, Yokohama, 226-8503, Japan. Tomoteru Fukumura1, Masashi Kawasaki1 Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, 980-8577, Japan. Hideomi Koinuma1 Frontier Collaborative Research Center, Tokyo Institute of Technology, Midori-ku, Yokohama, 226-8503, Japan. 1 Combinatorial Materials Exploration and Technology (COMET), Namiki, Tsukuba, 305-0044, Japan. ABSTRACT The thermal diffusivities throughout a composition-spread film comprising La1-χSrχCoO3 series were determined by Transient Reflecting Grating (TRG) measurements. Thermal diffusivities of transparent SrCoO3 film and SrTiO3 substrate were determined by using third harmonics having wavelength of 266 nm as an excitation light with only a certain length of grating spacing. The thermal diffusivities of them were 0.02 and 0.05 cm2/s, respectively. With regard to untransparent thin films, the experiment was performed by setting three kinds of grating spacing for the excitation light having the fundamental wavelength, 800 nm in order to obtain high precision. The distribution profile of obtained values of the thermal diffusivity throughout the sample was traced as 0.06 - 0.18 - 0.01 cm2/s corresponding to the variation of χ in La1-χSrχCoO3, thus showing a convex profile, however, this anomalous profile was verified by comparing with the data obtained by the X-ray diffractometer. INTRODUCTION Recently much research effort has been focused on high-temperature superconductors and thermoelectric materials, the authors think, and it would be stressed that the birth of a unique, novel material would be given by a creative, novel process and analysis. Samples investigated in this research are of composite-spread film comprising La1-χSrχCoO3 series that are prepared by means of Composition Spread Method [1]. As the said film is a compositionally onedimensionally modulated film prepared over a substrate of SrTiO3 (100), its thermo-physical properties will be mapped out as functions of the doping concentration, χ. Hence, it is vitally important to determine its thermal diffusivity of a spot as tiny as nanometers in order to evaluate the thermo-physical properties of this material. With only a few applicable measurements, TRG based upon the principle of light pump-probe method, however, is a promising determination method [2-7]. The authors built up a thermal diffusivity determination system with a fundamental light-wavelength of 800 nm, and having a high space-resolution of 200 µm [6], and now enlarged the system so as to determinate the thermal diffusivity of samples such as the film S5.2.1
of SrCoO3 and the substrate of SrTiO3 which are transparent for the light havi
