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Title: Scanning tunneling microscopy contrast of isovalent impurities on the GaAs (110) surface explained with a geometrical model
Authors: Tilley, F. J.
Roy, Mervyn
Maksym, P. A.
Koenraad, P. M.
Krammel, C. M.
Ulloa, J. M.
First Published: 27-Jan-2016
Publisher: American Physical Society
Citation: Physical Review B, 2016, 93 (035313)
Abstract: Theoretical scanning tunneling microscopy (STM) images for all group-III and -V dopants on the GaAs (110) surface are calculated using density functional theory (DFT). In addition, a geometrical model based on the covalent radii of the dopants and substrate atoms is used to interpret the images. We find that the covalent radius of the dopant determines the geometry of the surface, which in turn determines the contrast seen in the STM images. Our model allows bond lengths to be predicted with an error of less than 4.2% and positions to be predicted with an average deviation of only 0.19 Å compared to positions from fully relaxed DFT. For nitrogen we demonstrate good qualitative agreement between simulated and experimental STM images for dopants located in the first three surface layers. We are able to explain differences in both the contrast and positions of bright and dark features in the STM image based on our geometrical model. We then provide a detailed quantitative analysis of the positions of the bright features for nitrogen dopants in the second layer. The agreement of the DFT calculation with experiment is excellent, with the positions of the peaks in simulated and experimental STM scans differing by less than 2% of the lattice constant. For dopants other than nitrogen, we compare the calculated STM image contrast with the available experimental data and again find good agreement.
DOI Link: 10.1103/PhysRevB.93.035313
ISSN: 1098-0121
eISSN: 1550-235X
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2016 American Physical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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