Optical transmission spectroscopy and spectroscopic ellipsometry were used to extract the optical properties of an epitaxially grown quasi-tetragonal thin film in the near infrared to near ultraviolet range. The absorption spectrum is overall blue shifted compared with that of rhombohedral , with an absorption onset near 2.25 eV, a direct 3.1 eV band gap, and charge transfer excitations that are higher than those of the rhombohedral counterpart. We interpret these results in terms of structural strain and local symmetry breaking.
REFERENCES
1.
J. H.
Haeni
, P.
Irvin
, W.
Chang
, R.
Uecker
, P.
Reiche
, Y. L.
Li
, S.
Choudhury
, W.
Tian
, M. E.
Hawley
, B.
Craigo
, A. K.
Tagantsev
, X. Q.
Pan
, S. K.
Streiffer
, L. Q.
Chen
, S. W.
Kirchoefer
, J.
Levy
, and D. G.
Schlom
, Nature (London)
430
, 758
(2004
).2.
K. J.
Choi
, M.
Biegalski
, Y. L.
Li
, A.
Sharan
, J.
Schubert
, R.
Uecker
, P.
Reiche
, Y. B.
Chen
, X. Q.
Pan
, V.
Gopalan
, L. -Q.
Chen
, D. G.
Schlom
, and C. B.
Eom
, Science
306
, 1005
(2004
).3.
K. M.
Rabe
, Curr. Opin. Solid State Mater. Sci.
9
, 122
(2005
).4.
A. M.
Kadomtseva
, A. K.
Zvezdin
, Y. F.
Popov
, A. P.
Pyatakov
, and G. P.
Vorob’ev
, JETP Lett.
79
, 571
(2004
).5.
T.
Zhao
, A.
Scholl
, F.
Zavaliche
, K.
Lee
, M.
Barry
, A.
Doran
, M. P.
Cruz
, Y. H.
Chu
, C.
Ederer
, N. A.
Spaldin
, R. R.
Das
, D. M.
Kim
, S. H.
Baek
, C. B.
Eom
, and R.
Ramesh
, Nature Mater.
5
, 823
(2006
).6.
H. W.
Jang
, S. H.
Baek
, D.
Ortiz
, C. M.
Folkman
, C. B.
Eom
, Y. H.
Chu
, P.
Shafer
, R.
Ramesh
, V.
Vaithyanathan
, and D. G.
Schlom
, Appl. Phys. Lett.
92
, 062910
(2008
).7.
J.
Wang
, J. B.
Neaton
, H.
Zheng
, V.
Nagarajan
, S. B.
Ogale
, B.
Liu
, D.
Viehland
, V.
Vaithyanathan
, D. G.
Schlom
, U. V.
Waghmare
, N. A.
Spaldin
, K. M.
Rabe
, M.
Wuttig
, and R.
Ramesh
, Science
299
, 1719
(2003
).8.
T.
Choi
, S.
Lee
, Y. J.
Choi
, V.
Kiryukhin
, and S. -W.
Cheong
, Science
324
, 63
(2009
).9.
S. Y.
Yang
, L. W.
Martin
, S. J.
Byrnes
, T. E.
Conry
, S. R.
Basu
, D.
Paran
, L.
Teichertz
, J.
Ihlefeld
, C.
Adamo
, A.
Melville
, Y. -H.
Chu
, C. -H.
Yang
, J. L.
Musfeldt
, D. G.
Schlom
, J. W.
Ager
III, and R.
Ramesh
, Appl. Phys. Lett.
95
, 062909
(2009
).10.
R. J.
Zeches
, M. D.
Rossell
, J. X.
Zhang
, A. J.
Hatt
, Q.
He
, C. -H.
Yang
, A.
Kumar
, C. H.
Wang
, A.
Melville
, C.
Adamo
, G.
Sheng
, Y. -H.
Chu
, J. F.
Ihlefeld
, R.
Erni
, C.
Ederer
, V.
Gopalan
, L. Q.
Chen
, D. G.
Schlom
, N. A.
Spaldin
, L. W.
Martin
, and R.
Ramesh
, Science
326
, 977
(2009
).11.
The true symmetry of the strain-stabilized phase that is the subject of this paper is monoclinic, but it’s a different phase than the isostructural (also monoclinic) distorted rhombohedral phase that as been widely studied in thin film form (Refs. 4–9 and 17–20). As one is a slight monoclinic distortion from tetragonal and the other a slight monoclinic distortion from rhombohedral (Ref. 10), we refer to these two distinct phases as simply tetragonal and rhombohedral , which is an oversimplification.
12.
P.
Fischer
, M.
Polomska
, I.
Sosnowska
, and M.
Szymanskig
, J. Phys. C
13
, 1931
(1980
).13.
F.
Kubel
and H.
Schmid
, Acta Crystallogr., Sect. B: Struct. Sci.
46
, 698
(1990
).14.
H. M.
Tütüncü
and G. P.
Srivastava
, Phys. Rev. B
78
, 235209
(2008
).15.
D.
Ricinschi
, K. -Y.
Yun
, and M.
Okuyama
, J. Phys.: Condens. Matter
18
, L97
(2006
).16.
K. Y.
Yun
, D.
Ricinschi
, T.
Kanashima
, M.
Noda
, and M.
Okuyama
, Jpn. J. Appl. Phys., Part 2
43
, L647
(2004
).17.
S. R.
Basu
, L. W.
Martin
, Y. H.
Chu
, M.
Gajek
, R.
Ramesh
, R. C.
Rai
, X.
Xu
, and J. L.
Musfeldt
, Appl. Phys. Lett.
92
, 091905
(2008
).18.
X. S.
Xu
, T. V.
Brinzari
, S.
Lee
, Y. H.
Chu
, L. W.
Martin
, A.
Kumar
, S.
McGill
, R. C.
Rai
, R.
Ramesh
, V.
Gopalan
, S. -W.
Cheong
, and J. L.
Musfeldt
, Phys. Rev. B
79
, 134425
(2009
).19.
J. F.
Ihlefeld
, N. J.
Podraza
, Z. K.
Liu
, R. C.
Rai
, X.
Xu
, T.
Heeg
, Y. B.
Chen
, J.
Li
, R. W.
Collins
, J. L.
Musfeldt
, X. Q.
Pan
, J.
Schubert
, R.
Ramesh
, and D. G.
Schlom
, Appl. Phys. Lett.
92
, 142908
(2008
).20.
A.
Kumar
, R. C.
Rai
, N. J.
Podraza
, S.
Denev
, M.
Ramirez
, Y. H.
Chu
, L. W.
Martin
, J.
Ihlefeld
, T.
Heeg
, J.
Schubert
, D. G.
Schlom
, J.
Orenstein
, R.
Ramesh
, R. W.
Collins
, J. L.
Musfeldt
, and V.
Gopalan
, Appl. Phys. Lett.
92
, 121915
(2008
).21.
22.
H.
Fujiwara
, Spectroscopic Ellipsometry: Principles and Applications
(Wiley
, West Sussex, England
, 2007
).23.
M.
Tinkham
, in Far Infrared Properties of Solids
, edited by S. S.
Mitra
and S.
Nudelman
(Plenum
, New York
, 1970
), p. 233
.24.
C.
Chen
, I.
An
, G. M.
Ferreira
, N. J.
Podraza
, J. A.
Zapien
, and R. W.
Collins
, Thin Solid Films
455-456
, 14
(2004
).25.
J. B.
Neaton
, C.
Ederer
, U. V.
Waghmare
, N. A.
Spaldin
, and K. M.
Rabe
, Phys. Rev. B
71
, 014113
(2005
).26.
X. S.
Xu
, J. H.
Lee
, J.
Ihlefeld
, A.
Kumar
, R.
Ramesh
, V.
Gopalan
, D. G.
Schlom
, and J. L.
Musfeldt
, “Tunable band gap in films
” (unpublished).27.
Y.
Cong
, I.
An
, K.
Vedam
, and R. W.
Collins
, Appl. Opt.
30
, 2692
(1991
).28.
H.
Fujiwara
, J.
Koh
, P. I.
Rovira
, and R. W.
Collins
, Phys. Rev. B
61
, 10832
(2000
).29.
G. E.
Jellison
, Jr. and F. A.
Modine
, Appl. Phys. Lett.
69
, 371
(1996
).30.
R. W.
Collins
and A. S.
Ferlauto
, in Handbook of Ellipsometry
, edited by H. G.
Tompkins
and E. A.
Irene
(William Andrew
, Norwich, NY
, 2005
), pp. 125
–129
.© 2010 American Institute of Physics.
2010
American Institute of Physics
You do not currently have access to this content.
