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04/22/23 1
Hard X-ray Photoelectron Spectroscopy (HAXPES)
Of Correlated Materials A. Chainani,1,2 Y. Takata,1* M. Oura,2
AcknowledgementsFor the development of HAXPES @ BL29XU
Coherent X-ray Optics Lab. @ RIKEN SPring8 CenterM. Yabashi, K. Tamasaku, Y. Nishino, D. Miwa, T. Ishikawa
JASRI/SPring-8E. Ikenaga (BL47XU), K. Kobayashi ( BL15XU, NIMS)
HiSOR, Hiroshima Univ.M. Arita, K. Shimada, H. Namatame, M. Taniguchi
Musashi Inst. TechnologyH. Nohira, T. Hattori (Tohoku Univ.)
VG SCIENTA
04/22/23 4
AcknowledgementsFor Collaborations
Titanates H. Hwang, H. Takagi Vanadates H. Hwang, K Motoya, Z HiroiManganites M. Oshima, Y. TokuraCobaltates E. Takayama-MuromachiCuprates T. Mochiku, K Hirata Ruthenates A. YamamotoCe compounds H. SugawaraYb compounds N. Tsujii, A. Ochiai, S NakatsujiNitrides K. Takenaka
3) Applications : Strongly correlated electron systems
4) Future directions
5) Summary
04/22/23 6
Main Characteristic of HAXPES
IMFPs 1-4nm @ 1 keV 7-20nm @ 8 keV
Inelastic Mean Free Path (IMFP) of Electron(From NIST Database)
0 2000 4000 6000 8000 100000
50
100
150
200
250
Si
NaCl
SiO2
GaAs
Au
Electron Kinetic Energy (eV)
Inela
stic
Mean
Pat
h (
A)
30Å( SiO2)
210Å( SiO2)
140Å(SiO2)
Al KBulk sensitiveFree from surface prep.Functional thin filmsChemical depth analysisEmbedded interfaces (non destructive)
Large probing depth!
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Early HAXPES with Cu K@8keV
S. Hagstrom, C. Nordlimg, Chuck Fadley, S. Hagstrom, J. Hollander,K. Siegbahn, Phys. Lett. 9, 235 (1964) M. Klein, D. A. Shirley, Science 157, 1571 (1967)
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The first HAXPES with SR I. Lindau, P. Pianetta, S. Doniach & W E Spicer, Nature 250, 214 (1974)
Au 4fcore level: possiblevalence band: impossible
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0 10 20 30 40 50 60 70 80 901E- 8
1E- 7
1E- 6
1E- 5
1E- 4
1E- 3
0.01
0.1
1
10
Atomic Number ab
s (M
b/at
om
) at
1.0
4 K
eV
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d 4f 6p
0 10 20 30 40 50 60 70 80 901E- 8
1E- 7
1E- 6
1E- 5
1E- 4
1E- 3
0.01
0.1
1
10
abs
(Mb/
atom
) at
8.0
5 K
eV
Atomic Number
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d 4f 6p
Small photoionization Cross Sections
Obstacle to development of HAXPES
Rapid decrease!~ 1/100
1keV
8keV
04/22/23 10
High-energy Ce-3d photoemission: Bulk properties of CeM2 (M=Fe,Co,Ni) and Ce7Ni3 L. Braicovich, N. B. Brookes, C. Dallera, M. Salvietti, and G. L. OlcesePhys. Rev. B 56, 15047 (1997) @ESRFHigh-energy resonant photoemission and resonant Auger spectroscopy in Ce-Rh compounds @ESRFP. Le Fèvre, H. Magnan, D. Chandesris, J. Vogel, V. Formoso, and F. CominPhys. Rev. B 58, 1080 (1998) Hybridization and Bond-Orbital Components in Site-Specific X-Ray Photoelectron Spectra of Rutile TiO2 @NSLSJ. C. Woicik, E. J. Nelson, Leeor Kronik, Manish Jain, James R. Chelikowsky, D. Heskett, L. E. Berman, and G. S. Herman, Phys. Rev. Lett. 89, 077401 (2002)Quadrupolar Transitions Evidenced by Resonant Auger Spectroscopy @HASYLABJ. Danger, P. Le Fèvre, H. Magnan, D. Chandesris, S. Bourgeois, J. Jupille, T. Eickhoff, and W. Drube, Phys. Rev. Lett. 88, 243001 (2002)
Looking 100 Å deep into spatially inhomogeneous dilute systems with hard x-ray photoemission @ESRF C Dallera, L. Duò, L. Braicovich, G. Panaccione, G. Paolicelli, B. Cowie, and J. Zegenhagen Appl. Phys. Lett. 85, 4532 (2004)
High resolution-high energy x-ray photoelectron spectroscopy using third-generation synchrotron radiation source, and its application to Si-high k insulator systems @SPring8K. Kobayashi et al. Appl. Phys. Lett. 83, 1005 (2003)A probe of intrinsic valence band electronic structure: Hard x-ray photoemission @SPring8Y. Takata et al. Appl. Phys. Lett. 84, 4310 (2004) HAXPES for Valence Bands with
h = 6 – 8 KeV.
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Experimental Setup
How to gain in stability, resoluton, photoelectron intensity 1. High brilliance SR at SPring-8 2. High performance analyzer
3. Top-up injection4. Matching the detection angle to the polarization of SR
magic angle
For linearly polarized light, angular intensity distribution of photoemitted electrons depends on the asymmetry parameter >0 at energies of several keV, for almost all subshells
J.Yeh & I.Lindau At. Data.Nucl Data Tables 32, 1(1985)Their intensities have a maximum in a direction parallel to the electric polarization vector
Contribution of surface SiO2 is negligible!IMFP: Si=12nm, SiO2=16nm @ 8keV Si=1.8nm, SiO2=3nm @ 0.85keV
20 15 10 5 0
@7.94keV(Exp.)
@0.85keV(Exp.)
SiO2-0.58nm/Si(100)
Nor
mal
ized
Inte
nsity
Binding Energy (eV)
300sec
SiO2
7830 7835 7840
Si
SiO2x 10
SiO2-0.8nm/Si(100)
Inte
nsity
Kinetic Energy (eV)6090 6095 6100
0
SiO2-0.8nm/Si(100) Si
SiO2x 10
Inte
nsity
Kinetic Energy (eV)
Si 1sBE:1840eV
Si 2pBE:100eV10sec 30sec
Si : SiO2=42 : 1SiO2 contribution < 3%
Y. Takata et al. Appl. Phys. Lett. 84, 4310 (2004)
04/22/23 20
Effect of Grazing Incidence of X-raysEffect of Grazing Incidence of X-rays
see also V Strocov, condmat/2013
04/22/23 21
High SensitivityHigh Sensitivity(Buried Layer and Interface)(Buried Layer and Interface)
SrTiO3
LaVO3:3MLLaAlO3:3ML
LaAlO3:30ML
2465 2470 2475
h=7.94 keV
V 1s (BE:5467eV)
Pho
toel
ectr
on In
tens
ityKinetic Energy (eV)
H. Wadati, A. Fujimori, H. Y. Hwang et al., PRB77, 045122 (2008)
0 10 20 30 40 50 60 70 80 901E- 8
1E- 7
1E- 6
1E- 5
1E- 4
1E- 3
0.01
0.1
1
10
abs
(Mb/at
om
) at
8.0
5 K
eV
Atomic Number
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d 4f 6p
5x10-7 Mb
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Large Probing DepthLarge Probing Depth
4015 4010 4005
Nor
mal
ized
Inte
nsity
Kinetic Energy (eV)
Sr 2p3/2 (BE=1940eV)
x65
e-e-
La0.85Ba0.15MnO3 (20nm)SrTiO3
H. Tanaka et al.,Phys. Rev. B 73, 094403
(2006)
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Applications
La1-xSrxMnO3 M-I transition with Colossal magnetoresistance
A.Urushibara et al., Phys. Rev. B 51, 14103 (1995)
H. Fujishiro et al., J. Phys. Soc. Jpn. 67, 1799 (1998)
Feature absent in earlier soft-ray PES
A.Chainani et al. Phys. Rev. B 47, 15397 (1993)
T.Saitoh et al., Phys. Rev. B 56, 8836 (1997)
MO6 Cluster model calculations
Ground state : linear combination of 6 configurations
3d6L2
3d6LC3d5C
3d6C2
U
F
O 2p band
UH
LH
1. Intra-atomic multiplets
2. Crystal Field
3. Hybridization between O 2p and Ru 3d orbital : Covalency
4 . Hybridization between coherent states at EF and Ru 3d orbitals : metallicity
3d4 3d5L
M. Taguchi
G. Van der Laan et al PRB 23, 4369(1981)J. Imer & E. Wuilloud. Z Phys. B66, 153 (1987) 21
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Comparison with cluster calculations
V* = 0.28VΔ* = 3.6 eV
V* = 0.39VΔ* = 4.0 eV
V* = 0.425VΔ* = 4.0 eV
V* = 0.25VΔ* = 3.0 eV
FM
AFM
FM
AFI
Good agreement!
low BE feature
CT from coherent states
2p53d5C
K. Horiba et al.Phys. Rev. Lett 93, 236401 (2004)
V1.98Cr0.02O3 (experiments)
Metal
Insulator
K. Smith et al. PRB 50, 1382 (1994)
(h = Al K :1486.7 eV)
M. Taguchi et al.PRB 71,155102(2005)
(h : 5950 eV)
V2O3 VB Photoemission (Coherent Peak)
Mo et al. PRL 90, 186403 (2003)
Zhang et al. PRL 70, 1666 (1993)
Coherent part
Incoherent part
U
DMFT cal.
Calculation vs. Experiment
*- Udc|
2p53dL
2p53d3C
2p53d2
-Udc|
*
3d3L
3d3C
3d2
| g > |f >
M. Taguchi et al.PRB 71,155102(2005)
Hole- and Electron-Doped High-Tc Cuprates
La2CuO4 Nd2CuO4
* M. van Veenendaal et al. PRB 49, 1407 (1994)
* Ino et al., PRL 79, 2101 (1997)* Harima et al., PRB 64, 220507(R) (2001)
* Steeneken et al. PRL 90, 247005 (2003)
Background ( doping induced chemical potential shift)
Mid-gap pinning scenario
Crossing the gap scenario
formation of new states within the band gap on doping
M. van Veenendaal et al. PRB 49, 1407 (1994)
moves to the top of the valence band by hole-doping and bottom of the conduction band on electron-doping
Calculation vs. Experiment
*- Udc|
2p53d9
-Udc|
*
3d10L
3d10C
3d9
| g > | f >
2p53d10L
2p53d10C
M. Taguchi et al.Phys. Rev. Lett. 95, 17702 (2005).
Cu 2p XPS (Estimated Parameters)
F
O 2p band
UHB
NCCO
F
O 2p band
UHB
LSCO
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CT type system: Nd1.85Ce0.15CuO4 (NCCO) M. Taguchi et al., Phys. Rev. Lett. 95, 17702 (2005).
1.5keV5.9keV
See also G. Panaccione et al. PRB 77, 125133 (2008)
U F
UH
LHO 2p band
Charge-Transfer type
04/22/23 38
Valence Transition of YbInCu4
800eV43eV
5950eV
See also Suga et al., J. Phys. Soc. Jpn, 78, 074704 (2009)
H. Sato et al., Phys. Rev. Lett., 93, 246404 (2004)
04/22/23 39
Combining HAXPES with optical spectroscopyEvidence for purely Yb2+ bulk state, Yb3+ surface state,
and energy-loss satellite due to interband transitions
However, the Yb valence estimated by L-edge RIXS & XAS:~2.08 K. Syassen, Physica B+C 139-140 (1986) 277.
~2.35 E. Annese et al., Phys. Rev. B 70 (2004) 075117.
YbS: Ionic crystal Yb2+S2-, hence typical Yb2+ system
Inte
nsit
y (a
rb. u
nits
)
1600 1580 1560 1540 1520Binding Energy (eV)
YbS
YbCu2Si2T = 20 K
Yb 3dh = 7.94 keV
Yb3+ Yb2+Yb3+ Yb2+
T = 300 K
= 0°
= 80°
= 0°
he-
Inte
nsit
y (a
rb. u
nits
)30 20 10 0 -10
Relative Energy (eV)
1550 1540 1530 1520Binding Energy (eV)
YbS Yb 3d5/2
= 80°
× 3 = 0°
Loss Function [Im(1/)]
opticalreflectivity
M. Matsunami et al., Phys. Rev. B, 78, 185118(2008)
04/22/23 40
Remote hole-doping at an interfaceM. Takizawa et al., PRL. 102, 236401(2009)
V3+(bulk)
For LaAlO3/SrTiO3, see M. Sing et al. PRL 102, 176805 (2009)
Science, 291, 854 (2001)
• Electronic structure of the room temperature ferromagnet Co:TiO2 anatase
04/22/23 41
Nature Materials 4,173(2005)
Carriers : hydrogenic type04/22/23 42
Core level spectra
Al K XPSJ W Quilty et alPRL 96, 027202(2006)
T. Ohtsuki et alPRL 106,047602(2011)04/22/23 43
Valence band spectra CoO/Co metal
J W Quilty et alPRL 96, 027202(2006)
04/22/23 44
J. Woicik et al Phys. Rev. Lett. 89, 077401(2002)04/22/23 45
Co 2p-3d XAS
04/22/23 46
Co 2p-3d Resonant PES
04/22/23 47
Ti 2p-3d Resonant PES
Coherent +Incoherent
feature
T. Ohtsuki et alPRL 106,047602(2011)
04/22/23 48
04/22/23 49
charge neutrality condition : Co2+ + VO 2− + 2Ti 4+ Co 2+ + 2Ti 3+
(VO is oxygen vacancy)
Surface Science, 601, 5034(2007)
04/22/23 50
04/22/23 51
correspondence between the well-screened feature and coherent states
S. Biermann et al, PRL, 94, 026404,2005 ; J. M. Tomczak & S. Biermann, J. Phys.: Cond. Matter, 19, 365206, 2007.J. M. Tomczak, F. Aryasetiawan & Silke Biermann, PRB, 78,115103, 2008.
See also T. Koethe et al PRL 97, 166402(2006) ; S. Suga et al, New J. Physics 11, 103015 (2009).
Hg2Ru2O7 and Tl2Ru2O7 exhibit first order metal-insulator transitions(MIT)
• Hg2Ru2O7
• Tc = 108 K
• eff ~3.7B
• Ru 5+
• Tl2Ru2O7
• Tc = 125 K
• eff ~ 2.8B
• Ru 4+
A Yamamoto et al JPSJ(Letters) 4, 043703 (2007) S. Lee et al Nature Materials 5, 471 (2006)W. Klein et al J. Mat. Chemistry 17, 1356 (2007) 2