Metal oxides are typically insulating materials that can be made conductive through aliovalent doping and/or non-stoichiometry. Recent studies have identified conductive states at surfaces and interfaces of pure oxide materials; high electron concentrations are present, resulting in a high-mobility two-dimensional electron gas. We demonstrate for In2O3 that the energy required to form an oxygen vacancy decreases rapidly towards the (111) surface, where the coordination environment is lowered. This is a general feature of metal oxide systems that can result in a metal–insulator transition where donors are produced at chemically reduced extended defects.
REFERENCES
1.
J.
Mannhart
and D.
Schlom
, Science
327
, 1607
(2010
).2.
H.
Hwang
, Science
313
, 1895
(2006
).3.
A.
Santander-Syro
, O.
Copie
, T.
Kondo
, F.
Fortuna
, S.
Pailhes
, R.
Weht
, X.
Qiu
, F.
Bertran
, A.
Nicolaou
, and A.
Taleb-Ibrahimi
, Nature
469
, 189
(2011
).4.
P. D. C.
King
, T. D.
Veal
, D. J.
Payne
, A.
Bourlange
, R. G.
Egdell
, and C. F.
McConville
, Phys. Rev. Lett.
101
, 116808
(2008
).5.
P. D. C.
King
, T. D.
Veal
, C. F.
McConville
, J.
Zúñiga Pérez
, V.
Muñoz Sanjosé
, M.
Hopkinson
, E. D. L.
Rienks
, M. F.
Jensen
, and P.
Hofmann
, Phys. Rev. Lett.
104
, 256803
(2010
).6.
W.
Meevasana
, P. D. C.
King
, R. H.
He
, S.-K.
Mo
, M.
Hasimoto
, A.
Tamai
, P.
Songsiriritthigul
, F.
Baumberger
, and Z.-X.
Shen
, Nat. Mater.
10
, 114
(2011
).7.
E.
Dagotto
, Nature
469
, 167
(2011
).8.
K. H. L.
Zhang
, A.
Walsh
, C. R. A.
Catlow
, V. K.
Lazarov
, and R. G.
Egdell
, Nano Lett.
79
, 3740
(2010
).9.
A.
Walsh
and C. R. A.
Catlow
, J. Mater. Chem.
20
, 10438
(2010
).10.
V.
Blum
, R.
Gehrke
, F.
Hanke
, P.
Havu
, V.
Havu
, X.
Ren
, K.
Reuter
, and M.
Scheffler
, Comput. Phys. Commun.
180
, 2175
(2009
).11.
E.
van Lenthe
, E. J.
Baerends
, and J. G.
Snijders
, J. Chem. Phys.
101
, 9783
(1994
).12.
J. P.
Perdew
, A.
Ruzsinszky
, G. I.
Csonka
, O. A.
Vydrov
, G. E.
Scuseria
, L. A.
Constantin
, X.
Zhou
, and K.
Burke
, Phys. Rev. Lett.
100
, 136406
(2008
).13.
D. M.
Duffy
, J. P.
Hoare
, and P. W.
Tasker
, J. Phys. C
17
, 195
(1983
).14.
A.
Walsh
, C. R. A.
Catlow
, A. A.
Sokol
, and S. M.
Woodley
, Chem. Mater.
21
, 4962
(2009
).15.
J. D.
Gale
and A. L.
Rohl
, Mol. Simul.
29
, 291
(2003
).16.
A sheet donor density of 5 × 1012 cm−2 is distributed across the surface based on the calculated vacancy formation energies and T = 750 K. A rigorous approach requires temperature dependent defect free energies, which would enable quantitative predictions of equilibrium constants.
17.
S.
Lany
and A.
Zunger
, Phys. Rev. Lett.
106
, 069601
(2011
).18.
N. F.
Mott
, Rev. Mod. Phys.
40
, 677
(1968
).19.
P. P.
Edwards
and M. J.
Sienko
, Phys. Rev. B
17
, 2575
(1978
).20.
J.
Woning
and R. A.
Van Santen
, Chem. Phys. Lett.
101
, 541
(1983
).21.
A.
Migani
, G. N.
Vayssilov
, S. T.
Bromley
, F.
Illas
, and K. M.
Neyman
, J. Mater. Chem.
20
, 10535
(2010
).22.
X. T.
Sayle
, S. C.
Parker
, and C. R. A.
Catlow
, J. Chem. Soc., Chem. Commun.
1992
, 977
(1992
).23.
M.
Nolan
, J. E.
Fearon
, and G. W.
Watson
, Solid State Ionics
177
, 3069
(2006
).24.
C. R. A.
Catlow
, A. A.
Sokol
, and A.
Walsh
, Chem. Commun.
47
, 3386
(2011
).25.
W.
Walukiewicz
, Physica B
302–303
, 123
(2001
).26.
S. B.
Zhang
, S.-H.
Wei
, and A.
Zunger
, Phys. Rev. Lett.
84
, 1232
(2000
).© 2011 American Institute of Physics.
2011
American Institute of Physics
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