Submicron x-ray diffraction and its applications to problems in materials and environmental science

Abstract

The availability of high brilliance 3 rd generation synchrotron sources together with progress in achromatic focusing optics allow to add submicron spatial resolution to the conventional century-old X-ray diffraction technique. The new capabilities include the possibility to map in-situ, grain orientations, crystalline phase distribution and full strain/stress tensors at a very local level, by combining white and monochromatic X-ray microbeam diffraction. This is particularly relevant for high technology industry where the understanding of material properties at a microstructural level becomes increasingly important. After describing the latest advances in the submicron X-ray diffraction techniques at the ALS, we will give some examples of its application in material science for the measurement of strain/stress in metallic Work supported in part by the Department of Energy contract DE-AC03-76SF00515. August 2002 2 thin films and interconnects. Its use in the field of environmental science will also be discussed. KeywordsX-ray micro-diffraction, thin films, microtexture, strain/stress Contact Author Nobumichi Tamura, Lawrence Berkeley National Lab., MS 2-400, Berkeley, CA 94720, tel. (510) 486 6189, fax (510) 486 7696 e-mail: ntamura@lbl.gov Introduc tionMaterials properties such as strengthening, resistance to fatigue and failure intimately depend on their microstructural features such as grains, grain boundaries, inclusions, voids and other defects. However, at the so-called mesoscopic length scale (approximately between 0.1 and 10 microns) materials typically exhibit high inhomogeneity, and properties are extremely difficult to study both experimentally and theoretically. This length scale is situated between the atomic scale of atoms and individual dislocations, and the macroscopic scale of continuum mechanics.X-ray diffraction is a powerful technique, used for almost a century to measure grain orientation and strain, as well as for crystalline phase identification and structure refinement.Compared to electron microscopy, X-rays have the advantages of higher penetration depth (rendering possible the scanning of bulk and buried samples), do not require any particular sample preparation and can be used under a variety of different conditions (in air, liquid, 3 vacuum or gas, at different temperature and pressures). Its main drawback for the study of materials at the micron scale was until recently its poor spatial resolution.Today, the availability of high brilliance third generation synchrotron sources, combined with progress in X-ray focusing optics and fast 2D large area detector technology have made possible the development of Scanning X-ray Microdiffraction (µSXRD) techniques using either monochromatic or polychromatic focused beams of sizes ranging from a few microns to submicron [1][2][3][4][5][6][7][8]. The closest equivalents in the electron microscopy field are STEM (Scanning Transmission Electron Microscopy) and EBSD (Electron Back Scatter Diffraction).The spatial resolution of electron micr...

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