Results from electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) experiments are used to establish the model for the ground state of the singly ionized oxygen vacancy in the interior of bulk rutile TiO2 crystals. Hyperfine from 47Ti and 49Ti nuclei show that the unpaired electron in this S = 1/2 defect is localized on one titanium ion adjacent to the oxygen vacancy (i.e., the spin is not shared by two titanium ions). These defects are formed at low temperature (∼35 K) in as-grown oxidized crystals when sub-band-gap 442 nm laser light converts doubly ionized nonparamagnetic oxygen vacancies to the singly ionized paramagnetic charge state. The g matrix is obtained from EPR spectra and the 47Ti and 49Ti hyperfine and nuclear electric quadrupole matrices (A and Q) are obtained from ENDOR spectra. Principal values of the 47Ti and 49Ti hyperfine matrices are 64.54, 11.57, and 33.34 MHz. All the matrices have a principal axis along the [001] direction. In the basal plane, principal axes of the hyperfine and quadrupole matrices also coincide. The principal axes of the g matrix in the basal plane, however, deviate significantly from those of the A and Q matrices, thus indicating mixing of d orbitals due to the low symmetry at the Ti3+ ion site and participation of excited-state orbitals.

1.
X. Y.
Pan
,
M. Q.
Yang
,
X. Z.
Fu
,
N. Z.
Zhang
, and
Y. J.
Xu
,
Nanoscale
5
,
3601
(
2013
).
2.
M. A.
Henderson
,
Surf. Sci. Rep.
66
,
185
(
2011
).
3.
A.
Fujishima
,
X.
Zhang
, and
D. A.
Tryk
,
Surf. Sci. Rep.
63
,
515
(
2008
).
4.
K.
Szot
,
M.
Rogala
,
W.
Speier
,
Z.
Klusek
,
A.
Besmehn
, and
R.
Waser
,
Nanotechnology
22
,
254001
(
2011
).
5.
J. J.
Yang
,
M. D.
Pickett
,
X.
Li
,
D. A. A.
Ohlberg
,
D. R.
Stewart
, and
R. S.
Williams
,
Nat. Nanotechnol.
3
,
429
(
2008
).
6.
7.
M.
Ménétry
,
A.
Markovits
,
C.
Minot
, and
G.
Pacchioni
,
J. Phys. Chem. B
108
,
12858
(
2004
).
8.
S.
Lany
and
A.
Zunger
,
Phys. Rev. B
72
,
035215
(
2005
).
9.
S.
Yang
,
L. E.
Halliburton
,
A.
Manivannan
,
P. H.
Bunton
,
D. B.
Baker
,
M.
Klemm
,
S.
Horn
, and
A.
Fujishima
,
Appl. Phys. Lett.
94
,
162114
(
2009
).
10.
Shan
Yang
, “
Paramagnetic resonance studies of defects in titanium dioxide crystals
,” Ph.D. dissertation (
West Virginia University
, Morgantown, WV,
2009
).
11.
F. D.
Brandão
,
M. V. B.
Pinheiro
,
G. M.
Ribeiro
,
G.
Medeiros-Ribeiro
, and
K.
Krambrock
,
Phys. Rev. B
80
,
235204
(
2009
).
12.
T. S.
Bjørheim
,
A.
Kuwabara
, and
T.
Norby
,
J. Phys. Chem. C
117
,
5919
(
2013
).
13.
A.
Janotti
,
C.
Franchini
,
J. B.
Varley
,
G.
Kresse
, and
C. G.
Van de Walle
,
Phys. Status Solidi (RRL)
7
,
199
(
2013
).
14.
P.
Deák
,
B.
Aradi
, and
T.
Frauenheim
,
Phys. Rev. B
86
,
195206
(
2012
).
15.
H.-Y.
Lee
,
S. J.
Clark
, and
J.
Robertson
,
Phys. Rev. B
86
,
075209
(
2012
).
16.
T. V.
Perevalov
and
V. A.
Gritsenko
,
J. Exp. Theor. Phys.
112
,
310
(
2011
).
17.
J.
Stausholm-Møller
,
H. H.
Kristoffersen
,
B.
Hinnemann
,
G. K. H.
Madsen
, and
B.
Hammer
,
J. Chem. Phys.
133
,
144708
(
2010
).
18.
G.
Mattioli
,
P.
Alippi
,
F.
Filippone
,
R.
Caminiti
, and
A. A.
Bonapasta
,
J. Phys. Chem. C
114
,
21694
(
2010
).
19.
B. J.
Morgan
and
G. W.
Watson
,
J. Phys. Chem. C
114
,
2321
(
2010
).
20.
S. G.
Park
,
B.
Magyari-Kope
, and
Y.
Nishi
,
Phys. Rev. B
82
,
115109
(
2010
).
21.
C.
Di Valentin
,
G.
Pacchioni
, and
A.
Selloni
,
J. Phys. Chem. C
113
,
20543
(
2009
).
22.
X.
Li
,
M. W.
Finnis
,
J.
He
,
R. K.
Behara
,
S. R.
Philpot
,
S. B.
Sinnott
, and
E. C.
Dickey
,
Acta Mater.
57
,
5882
(
2009
).
23.
T.
Minato
,
Y.
Sainoo
,
Y.
Kim
,
H. S.
Kato
,
K.
Aika
,
M.
Kawai
,
J.
Zhao
,
H.
Petek
,
T.
Huang
,
W.
He
,
B.
Wang
,
Z.
Wang
,
Y.
Zhao
,
J.
Yang
, and
J. G.
Hou
,
J. Chem. Phys.
130
,
124502
(
2009
).
24.
E.
Finazzi
,
C.
Di Valentin
,
G.
Pacchioni
, and
A.
Selloni
,
J. Chem. Phys.
129
,
154113
(
2008
).
25.
M.
Chiesa
,
M. C.
Paganini
,
S.
Livraghi
, and
E.
Giamello
,
Phys. Chem. Chem. Phys.
15
,
9435
(
2013
).
26.
S.
Livraghi
,
M.
Chiesa
,
M. C.
Paganini
, and
E.
Giamello
,
J. Phys. Chem. C
115
,
25413
(
2011
).
27.
S.
Livraghi
,
S.
Maurelli
,
M. C.
Paganini
,
M.
Chiesa
, and
E.
Giamello
,
Angew. Chem., Int. Ed.
50
,
8038
(
2011
).
28.
A. M.
Czoska
,
S.
Livraghi
,
M.
Chiesa
,
E.
Giamello
,
S.
Agnoli
,
G.
Granozzi
,
E.
Finazzi
,
C.
Di Valentin
, and
G.
Pacchioni
,
J. Phys. Chem. C
112
,
8951
(
2008
).
29.
M.
Aono
and
R. R.
Hasiguti
,
Phys. Rev. B
48
,
12406
(
1993
).
30.
S.
Yang
and
L. E.
Halliburton
,
Phys. Rev. B
81
,
035204
(
2010
).
31.
A. T.
Brant
,
S.
Yang
,
N. C.
Giles
, and
L. E.
Halliburton
,
J. Appl. Phys.
110
,
053714
(
2011
).
32.
A. T.
Brant
,
N. C.
Giles
, and
L. E.
Halliburton
,
J. Appl. Phys.
113
,
053712
(
2013
).
33.
S.
Yang
,
A. T.
Brant
,
N. C.
Giles
, and
L. E.
Halliburton
,
Phys. Rev. B
87
,
125201
(
2013
).
34.
S.
Watauchi
,
M. A. R.
Sarker
,
M.
Nagao
,
I.
Tanaka
,
T.
Watanabe
, and
I.
Shindo
,
J. Cryst. Growth
360
,
105
(
2012
).
35.
S. C.
Abrahams
and
J. L.
Bernstein
,
J. Chem. Phys.
55
,
3206
(
1971
).
36.
C. J.
Howard
,
T. M.
Sabine
, and
F.
Dickson
,
Acta Crystallogr., Sect. B: Struct. Sci.
47
,
462
(
1991
).
37.
K. H.
Channappa
and
J. M.
Pendlebury
,
Proc. Phys. Soc.
86
,
1145
(
1965
).
38.
H.
Rinneberg
and
J. A.
Weil
,
J. Chem. Phys.
56
,
2019
(
1972
).
39.
W. C.
Tennant
and
R. F. C.
Claridge
,
J. Magn. Reson.
137
,
122
(
1999
).
40.
M. M.
Abraham
,
Y.
Chen
,
L. A.
Boatner
, and
R. W.
Reynolds
,
Solid State Commun.
16
,
1209
(
1975
).
41.
A. M.
Stoneham
,
Theory of Defects in Solids
(
Clarendon Press
,
Oxford)
1975
, p.
465
.
42.
A. A.
Abragam
and
B. B.
Bleaney
,
Electron Paramagnetic Resonance of Transition Ions
(
Clarendon Press
,
Oxford)
1970
.
43.
J. R.
Pilbrow
and
M. R.
Lowrey
,
Rep. Prog. Phys.
43
,
433
(
1980
).
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