Unique x-ray diffraction pattern at grazing incidence from misfit dislocations in SiGe thin films

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.362776· OSTI ID:285535

Jordan-Sweet, J L; Mooney, P M; Lutz, M A; Feenstra, R M; Chu, J O; LeGoues, F K ^[1]

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1. IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (United States)

Grazing-incidence x-ray diffraction (GIXD) permits the direct measurement of in-plane lattice parameters of SiGe films that are too thin to yield good results from normal-geometry triple-axis techniques. A unique {open_quote}{open_quote}X{close_quote}{close_quote}-shaped pattern has been seen in {ital H}{endash}{ital K} reciprocal space maps of diffracted x-ray intensity from SiGe films that have relaxed via a modified Frank{endash}Read mechanism. Contours of intensity are seen along the {l_angle}110{r_angle} directions from the ({bar 4}00) reciprocal lattice peak with the introduction of the first dislocations. For higher dislocation densities the X-shaped contours are anisotropically distorted and a satellite peak, corresponding to the lattice parameter for a partially relaxed film, becomes identifiable at lower {ital H}. In contrast, {ital H}{endash}{ital K} reciprocal-space contours from thin SiGe films that have relaxed by roughening and subsequent random nucleation of dislocations display broad, oval-shaped contours centered at the ({bar 4}00) reciprocal lattice point for the film. Numeric simulations of GIXD from a variety of dislocation arrangements were performed in order to understand the origin of the X pattern. We show that this pattern arises from an array of long misfit dislocations running in the {l_angle}110{r_angle} directions. The anisotropic distortion of the X pattern arises at higher dislocation densities from orthogonal intersections of dislocations with equal Burgers vector, which are characteristic of dislocation networks generated by the modified Frank{endash}Read mechanism. We also verify that the measured values of the in-plane lattice parameter, together with the out-of-plane lattice parameter determined from the symmetric (004) reflection, lead to accurate calculation of the composition and strain in these SiGe layers. {copyright} {ital 1996 American Institute of Physics.}

• Research Organization: Brookhaven National Laboratory
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 285535
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 1 Vol. 80; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DISLOCATIONS
GERMANIUM SILICIDES
GRAZING
LATTICE PARAMETERS
MISFIT DISLOCATIONS
NUMERICAL SOLUTION
STRAINS
SYNCHROTRON RADIATION
THIN FILMS
X-RAY DIFFRACTION
XRD