High Throughput X-ray Diffractometer for Combinatorial Epitaxial Thin Films
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High Throughput X-ray Diffractometer for Combinatorial Epitaxial Thin Films M. Ohtani1), T. Fukumura2), A. Ohtomo1), T. Kikuchi3), K. Omote3), H. Koinuma1,4,5), M. Kawasaki1,2,5) 1) Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8503, Japan 2) Institute for Materials Research, Tohoku Univ., Sendai 980-8577, Japan 3) X-ray Research Laboratory, Rigaku Corporation, Akishima 196-8666, Japan 4) Frontier Collaborative Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan 5) Combinatorial Material Exploration and Technology (COMET), Tsukuba 305-8565, Japan ABSTRACT We report on the development of a high throughput x-ray diffractometer that concurrently measures spatially resolved x-ray diffraction (XRD) spectra of epitaxial thin films integrated on a substrate. A convergent x-ray is focused into a stripe on a substrate and the diffracted beam is detected with a two-dimensional x-ray detector, so that the snapshot image represents a mapping of XRD intensity with the axes of the diffraction angle and the position in the sample. High throughput characterization of crystalline structure is carried out for a BaxSr1-xTiO3 composition-spread film on a SrTiO3 substrate. Not only the continuous spread of the composition (x), but also the continuous spread of the growth temperature (T) are given to the film by employing a special heating method. The boundary between the strained lattice and relaxed lattice is visualized by the concurrent XRD as functions of x and T in a high throughput fashion. INTRODUCTION Recently, parallel synthesis of solid-state thin films having electronic, magnetic, and optical functionalities based on combinatorial methodology has attracted much attention for efficient materials discovery1,2. By using combinatorial laser molecular beam epitaxy (CLMBE) technique, one can fabricate various epitaxial combinatorial chips which contain several superlattices with atomic-scale interface control3 or continuous composition–spread of component elements on a substrate4. For characterizing the crystal structure, x-ray diffraction (XRD) measurement is indispensable. However, it is very time-consuming or practically impossible to characterize the combinatorial chip by conventional XRD. Isaacs et al. has S3.8.1
reported on a demonstration by using a focused micro beam from a synchrotron radiation source to perform x-ray fluorescence spectroscopy, near-edge x-ray absorption spectroscopy and XRD5. However, the access to synchrotron radiation source is not easy for most of the people introducing the combinatorial concept to their research and department. Here, we report on the development of an XRD measurement system for the laboratory stand-alone use, named as concurrent XRD (CXRD) 6, that measures two-dimensional XRD image with the frame axes of position and diffraction angle, hence is useful for XRD measurement as a function of position. EXPERIMENT The left panel of Fig.1 shows a schematic diagram of CXRD. An 1.2kW copper rotating anode with a diameter of
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