Abstract
We perform a systematic investigation of (100) surfaces for rocksalt-structured group 2 metal oxides, namely MgO, CaO, SrO and BaO, using GGA and Hybrid-DFT exchange-correlation functionals. We examine the structural, energetic and electronic properties of the surfaces, with a specific focus on the surface ionisation potential and band bending; the latter of which we quantify by examining the density of states as a function of depth from the system surface. We report structural and energetic results in-line with previous experimental work when we use the Hybrid-DFT method, and for the electronic structure we find inequivalent band bending for the valence and conduction bands, which results in reduced ionisation potentials and the closure of the band gap at the surface when compared to bulk systems. We also report downward bending of the conduction band for MgO that brings it below the vacuum potential, unlike previous theoretical investigations, and thus indicates an origin of the positive electron affinity found in the experiment.
Original language | English |
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Pages (from-to) | 58-65 |
Number of pages | 8 |
Journal | Surface Science |
Volume | 642 |
DOIs | |
Publication status | Published - 1 Dec 2015 |
Bibliographical note
Funding Information:The authors acknowledge stimulating discussions with Daniel Deacon-Smith, John Buckeridge, Keith Butler and Aron Walsh. The work in this manuscript has been partly influenced by the early computational study on MgO by Vladimir Puchin and Lev Kantorovich [55] . AJL acknowledges the Ramsay Memorial Trust and University College London for the provision of a Ramsay Fellowship; DMF acknowledges support from Mexico: CONACYT, SEP and UJAT. AJL, CRAC and AAS acknowledge funding from EPSRC grants EP/IO30662/1 and EP/K038419/1 . The authors acknowledge the use of the following high-performance computing facilities, and associated support services, in the completion of this work: HECToR, via our membership of the UK HPC Materials Chemistry Consortium (EP/L000202); IRIDIS, provided by the Centre for Innovation; UCL Legion.
Publisher Copyright:
© 2015 The Authors. Published by Elsevier B.V.
Keywords
- Band-bending
- Ionisation potential
- Rocksalt oxides
- Surface rumpling
- Surface structure
ASJC Scopus subject areas
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry