Influence of Surface Relaxation and Multi-Dislocation Strain Field Interactions on X-Ray Topographic Images of Dislocati
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INFLUENCE OF SURFACE RELAXATION AND MULTI-DISLOCATION STRAIN FIELD INTERACTIONS ON X-RAY TOPOGRAPHIC IMAGES OF DISLOCATIONS IN SEMICONDUCTOR MATERIALS JUN WU-, THOMAS FANNING*, MICHAEL DUDLEY -, VIJAY SHASTRY* AND PETER ANDERSON" Dept. of Materials Science & Engineering, SUNY at Stony Brook, NY 11794; Dept. of Materials Science & Engineering, Ohio State University, Columbus Ohio 43210 ABSTRACT Analysis of the white beam synchrotron x-ray topographic contrast behavior of screw dislocations comprising slip bands in silicon, observed under low absorption conditions, is presented. For both individual and groups of dislocations, observed "Direct Image" contrast at the surface intersections of dislocation lines, on reflections for which g.b=0, could be accounted for using equi-misorientation contour analysis using displacement fields which take surface relaxation effects into account. This contrast is shown to be a sensitive function of the local stress environment. In addition, diffuse area contrast observed within and in the vicinity of slip bands on such reflections is also observed to be very sensitive to long range strain fields associated with adjacent slip bands and other defects in the local slip band environment. INTRODUCTION X-ray topographic contrast behavior of groups of dislocations under low absorption conditions is of interest both from a theoretical point of view, and from the point of view of defining the range of dislocation densities within which one can safely predict image contrast and thus make positive identification. This has applications in several important areas, including the study of the mechanisms of the early stages of plastic deformation of single crystals [1, 2], and the investigation of dislocation configurations created during Rapid Thermal Processing (RTP) of crystals in the semiconductor industry [3, 4, 5]. Despite such interest it has remained one of the areas of contrast theory that has received very little attention over the years. It is well known that the contrast of individual dislocations under low absorption conditions can be described quite accurately using the "Direct Image" model, originally proposed by Authier [6]. According to this model the dislocation behaves as a miniature "mosaic" crystal embedded in an otherwise perfect single crystal. Calculation of the size and shape of the mosaic region, on reflections for which g.b$0 (where g is the reciprocal lattice vector of the reflection, and b is the Burgers vector of the dislocation), and its projection in the direction of the diffracted beam, enables dislocation image widths to be predicted with reasonable accuracy [7]. Discrepancies between calculated and observed image widths were attributed variously to errors in experimental procedure, intermediary image contributions, and surface relaxation effects, the latter being neglected in the calculation of misorientation. On reflections for which g.b=0, displacement fields associated with a screw dislocation in an infinite crystal lead to zero values of calculated misorientat
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