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Title: Persistent monolayer-scale chemical ordering in Si{sub 1−x}Ge{sub x} heteroepitaxial films during surface roughening and strain relaxation

Chemical ordering in semiconductor alloys could modify thermal and electronic transport, with potential benefits to thermoelectric properties. Here, metastable ordering that occurs during heteroepitaxial growth of Si{sub 1−x}Ge{sub x} thin film alloys on Si(001) and Ge(001) substrates is investigated. A parametric study was performed to study how strain, surface roughness, and growth parameters affect the order parameter during the alloy growth. The order parameter for the alloy films was carefully quantified using x-ray diffraction, taking into account an often-overlooked issue associated with the presence of multiple spatial variants associated with ordering along equivalent <111> directions. Optimal ordering was observed in the films having the smoothest surfaces. Extended strain relaxation is suggested to reduce the apparent order through creation of anti-phase boundaries. Ordering surprisingly persists even when the film surface extensively roughens to form (105) facets. Growth on deliberately miscut Si(001) surfaces does not affect the volume-averaged order parameter but does impact the relative volume fractions of the equivalent ordered variants in a manner consistent with geometrically necessary changes in step populations. These results provide somewhat self-contradictory implications for the role of step edges in controlling the ordering process, indicating that our understanding is still incomplete.
Authors:
;  [1]
  1. Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)
Publication Date:
OSTI Identifier:
22493104
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ELECTRON TRANSFER; EPITAXY; GERMANIUM; GERMANIUM ALLOYS; HEAT TRANSFER; ORDER PARAMETERS; PARAMETRIC ANALYSIS; RELAXATION; ROUGHNESS; SEMICONDUCTOR MATERIALS; SILICON; SILICON ALLOYS; STRAINS; THERMOELECTRIC PROPERTIES; THIN FILMS; X-RAY DIFFRACTION