Photon Factory Activity Report 2005 #23 Part B (2006)
Electronic Structure of Condensed Matter

2C/2005G101,2005S2-002

Photoemission study of SrVO3 thin films
Masaru TAKIZAWA*1, 2Riichiro TAKAISHI2,1 Daisuke TOYOTA2, Koji
MAEKAWA1, 3
2
Hiroshi KUMIGASHIRA , Atsushi FUJIMORI, Masaharu OSHIMA5 , Mikk LIPPMAA ,4Masashi
KAWASAKI,andHideomi KOINUMA
1
Department of Physics and Department of Complexity Science and Engineering,
University of Tokyo, Kashiwa 277-8561, Japan2
DepartmentofApplied
Chemistry, University of Tokyo, Tokyo 113-8656, Japan
3
InstituteforSolidStatePhysics, University of Tokyo, Kashiwa 277-8581, Japan
4
Institute for Materials5 Research, Tohoku University, Sendai 980-8577, JapanNIMS, Tsukuba 305-0047, Japan
Introduction
Metal-insulator transition has been extensively studied
because of its fundamental importance as well as its close
relationship to interesting phenomena such as hightemperature superconductivity in cuprates and colossal
magnetoresistance in manganites [1]. Ca1-xSrxVO3 (CSVO)
is a typical bandwidth control system but remains metallicfor the entire x range. With Ca doping, ultra-violet
photoemission spectra of CSVO have shown the spectral
weight transfer from the coherent part to the incoherent
part [2], while using high photon energies there were nospectral weight transfer [3]. In bulk CSVO, therefore, it is
now well known that the surface electronic states are very
different from the bulk ones. Many studies were devoted
to investigate the real “bulk” electronic states [4-6], but
the problem remains highly controversial and further
studies are strongly required. In the present work we havefabricated a SrVO3 (SVO) thin film and studied its
electronic structure in detail by photoemission
spectroscopy (PES).
Experiment
A SVO thin film was fabricated in a laser MBE
chamber connected to a synchrotron radiation PES system
at BL-2C of Photon Factory [7]. The films were deposited
on Nb-doped TiO2-terminated SrTiO3 (001) substrates [8]o-9
at 900 C at an ultra high vacuum of ~10 Torr. Thefabricated SVO thin film was transferred into thephotoemission chamber under an ultrahigh vacuum of 1010Torr. The PES spectra were taken at room temperature
with the total energy resolution of 200 ~ 500 meVdepending on photon energies.
Results and Discussion
Figure1 (a) shows a valence-band spectrum taken at hν
= 600 eV. The band between -10 eV to -3 eV is mainlycomposed of O 2p states and that between -3 eV to EF ismainly of V 3d states. In the V 3d band, there were two
features: the coherent part (the quasiparticle band nearEF) and the incoherent part (the remnant of the lower
Hubbard band). The intensity ratio of the coherent part tothe incoherent part was similar to that of the “bulk”
spectra in Refs. [3] and [5]. We further investigated thephoton-energy and emission-angle dependence (Fig. 1 (b)(c)). In the V 3d band, there were no significant
dependencies both on the photon energy and the emission
angle, indicating that the surface state little affects the V
3d band in the SVO thin film.

Figure1: Valence-band spectra of SrVO3 thin film. (a):Wide range spectrum taken at hν = 600 eV. (b): Photon
energy dependence. (c): Emission angle dependence.
References[1] M. Imada, A. Fujimori, and Y. Tokura, Rev. Mod. Phys.
70 1039 (1998), and references therein.
[2] I. H. Inoue et al., Phys. Rev. Lett. 74, 2539 (1995).
[3] A. Sekiyama et al., Phys. Rev. Lett. 93, 156402 (2004).
[4] R. Eguchi et al., Phys. Rev. Lett. 96, 076402 (2006).
[5] K. Maiti et al., Phys. Rev. B 73, 052508 (2006).
[6] T. Yoshida et al., Phys. Rev. Lett. 95, 146404 (2006).
[7] K. Horiba et al., Rev. Sci. Instr. 74, 3406 (2003).
[8] M. Kawasaki et al., Science 266, 1540 (1994).
*takizawa@wyvern.phys.s.u-tokyo.ac.jp

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