Edge-to-edge matching in thin films
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I. INTRODUCTION
IT is the aim of this article to summarize recent observations on the structure of hetero-interfaces between a thin, polycrystalline film and a single crystal substrate. The film consists of a single layer of grains that is formed by a solidstate reaction. While parts of this work have recently been published in journals that target an audience in the applied physics and thin film research communities,[1–4] it is our hope that the present summary in these proceedings of the Hume-Rothery Symposium 2004 may be of interest to the community of metallurgists. A. The Potential Relevance of Thin Film Results for Bulk Metallurgy The experimental characterization of interfaces is a difficult task. One may consider the example of a precipitate embedded within a polycrystalline host material. To study the precipitate boundary, one has to determine the orientation of the neighboring matrix with respect to the laboratory frame of reference (3 deg of freedom), the orientation of the precipitate (3 deg of freedom), and the orientation of the boundary plane (2 deg of freedom). Although orientation imaging microscopy or high-resolution transmission electron microscopy can be used to identify the orientation of single grains, it is difficult to obtain information for a statistically significant number of boundaries in this way. In this work, we propose a different approach: instead of studying precipitates embedded within their host matrix, we study the heterophase boundary between a thin film (consisting of a single layer of grains) and a single crystal substrate. The main advantage of this approach is a reduction in the number of degrees of freedom needed to describe the boundary, thus enabling the simultaneous acquisition of orientation information for a large number of grains by standard pole figure measurements. It may be argued that
C. DETAVERNIER is with the Department of Solid State Physics, Ghent University, 9000 Ghent, Belgium. Contact e-mail: christophe.detavernier @ugent.be C. LAVOIE is with the T.J. Watson Research Center, IBM, Yorktown Heights, New York, NY 10598, U.S.A. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. METALLURGICAL AND MATERIALS TRANSACTIONS A
thin films could potentially be used as model systems to study boundaries in bulk samples. The proposed approach reduces the number of degrees of freedom to only three. Since all of the heterophase interfaces are formed in contact with the same single crystal substrate, the orientation of the “matrix” is fixed. Second, since the film is either formed by deposition or by diffusion-controlled growth during a solid-state reaction, the boundary between film and substrate is usually parallel to the initial surface of the single crystal
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