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Why Are Polar Surfaces of ZnO Stable?

Mora-Fonz, D; Lazauskas, T; Farrow, MR; Catlow, CRA; Woodley, SM; Sokol, AA; (2017) Why Are Polar Surfaces of ZnO Stable? Chemistry of Materials , 29 (12) pp. 5306-5320. 10.1021/acs.chemmater.7b01487. Green open access

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Abstract

We probe and rationalize the complex surface chemistry of wurtzite ZnO by employing interatomic potential calculations coupled with a Monte Carlo procedure that sampled over 0.5 million local minima. We analyze the structure and stability of the (0001) and (0001̅) ZnO surfaces, rationalizing previous patterns found in STM images and explaining the (1 × 1) periodicity reported by LEED analysis. The full range of Zn/O surface occupancies was covered for a (5 × 5) supercell, keeping |mZn – mO|/N ≈ 0.24 where m and N are the numbers of occupied surface sites and total surface sites, respectively. Our calculations explain why the (5 × 5) reconstructions seen in some experiments and highlight the importance of completely canceling the inherent dipole of the unreconstructed polar surfaces. The experimentally observed rich reconstruction patterns can be traced from the lowest occupancy, showing the thermodynamically most stable configurations of both polar surfaces. Triangular and striped reconstructions are seen, inter alia, on both polar surfaces, and hexagonal patterns also appear on the O terminated surface. Our results explain the main experimental structures observed on these complex surfaces. Moreover, grand canonical simulations of ZnO polar surfaces reveal that disorder is favored and, thus, configurational entropic factors is the the cause of their stability.

Type: Article
Title: Why Are Polar Surfaces of ZnO Stable?
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.chemmater.7b01487
Publisher version: http://doi.org/10.1021/acs.chemmater.7b01487
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1561005
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