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04/11/23 1
Hard X-ray Photoelectron Spectroscopy (HAXPES)
Of Correlated Materials A. Chainani,1,2 Y. Takata,1* M. Oura,2
M. Taguchi,3 M. Matsunami,3 R. Eguchi,3 S. Shin,3
1 Coherent X-ray Optics Lab2 Advanced Photon Technology Division
3 Soft X-ray Spectroscopy Lab
RIKEN Harima Institute @ SPring-8
*deceased
04/11/23 2
04/11/23 3
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
04/11/23 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
04/11/23 5
Outline
1) Introduction
2) Experimental Setup, Performance & Characteristics
3) Applications : Strongly correlated electron systems
4) Future directions
5) Summary
04/11/23 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!
04/11/23 7
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)
04/11/23 8
The first HAXPES with SR I. Lindau, P. Pianetta, S. Doniach & W E Spicer, Nature 250, 214 (1974)
Au 4fcore level: possiblevalence band: impossible
04/11/23 9
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
04/11/23 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.
04/11/23 11
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
0
1
2
3
0
30
6090
120
150
180
210
240270
300
330
0
1
2
3
value
electricvector
-1 -0.5 0 0.5 1 1.5 2
5. Grazing incidence of X-rays
IMFP10nm rangee-
attenuation length 10m range
X-ray1 deg.
6. Well-focused X-ray beam 7. Low emittance operation
Pol.
55m(V)35m(H)
1deg.
04/11/23 13
Experimental setup at BL29XU in SPring-8Experimental setup at BL29XU in SPring-8
★ excitation energy: 5.95 or 7.94keV, E (h): 55 meV ★ photon flux: ~5x1011 photons/sec @ 55(V)x 35(H) m2
★ analyzer:R4000-10kV (VG Scienta)
Y. Takata et al., Nuclear Instrum. and Methods A547, 50 (2005).T. Ishikawa et al., Nuclear Instrum. and Methods A547, 42 (2005).
He flow cryostat to reduce sample vibration
04/11/23 14
Optics Layout for the HAXPES experiments
04/11/23 15
VOLPE @ESRF
P. Torelli et al., Rev. Sci. Instrum. 76, 023909 (2005)
30 sec
5 sec
High Energy Resolution & High ThroughputHigh Energy Resolution & High Throughput(at 7.94 keV)(at 7.94 keV)
E=55±5 meV (Ep=50 eV)E/E=140000!
15min
04/11/23 16
P. Torelli et al., Rev. Sci. Instrum. 76, 023909 (2005)
VOLPE@ ESRF
04/11/23 17
F. Schafers et al., Rev. Sci. Instrum. 78, 123102 (2007)
KMC-1@ BESSY-II
04/11/23 18
Au 4f core levels @ BESSY-II
04/11/23 19
Surface InsensitivitySurface InsensitivitySiOSiO22/Si(100) @ 7.94keV/Si(100) @ 7.94keV
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)
04/11/23 20
Effect of Grazing Incidence of X-raysEffect of Grazing Incidence of X-rays
see also V Strocov, condmat/2013
04/11/23 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
04/11/23 22
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)
04/11/23 23
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
04/11/23 29
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
04/11/23 37
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
04/11/23 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)
04/11/23 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)
04/11/23 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
04/11/23 41
Nature Materials 4,173(2005)
Carriers : hydrogenic type04/11/23 42
Core level spectra
Al K XPSJ W Quilty et alPRL 96, 027202(2006)
T. Ohtsuki et alPRL 106,047602(2011)04/11/23 43
Valence band spectra CoO/Co metal
J W Quilty et alPRL 96, 027202(2006)
04/11/23 44
J. Woicik et al Phys. Rev. Lett. 89, 077401(2002)04/11/23 45
Co 2p-3d XAS
04/11/23 46
Co 2p-3d Resonant PES
04/11/23 47
Ti 2p-3d Resonant PES
Coherent +Incoherent
feature
T. Ohtsuki et alPRL 106,047602(2011)
04/11/23 48
04/11/23 49
charge neutrality condition : Co2+ + VO 2− + 2Ti 4+ Co 2+ + 2Ti 3+
(VO is oxygen vacancy)
Surface Science, 601, 5034(2007)
04/11/23 50
04/11/23 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
Cleartemperaturedependenceacross the MIT
Compound Metallic bonding energy (kcal/mol)
Covalent bonding energy (kcal/mol)
Reference No.
Tl2Ru(IV)2O7 12.60 50.73 present workHg2Ru(V)2O7 21.68 46.12 present workTi4O7 20.06 66.88 44VO2 11.07 55.34 45V2O3 17.29 66.88 22CrN 17.53 62.26 46La0.8Sr0.2MnO3 9.80 67.80 30La0.85Ba0.15MnO3 9.22 67.80 47La1.85Sr0.15CuO4 28.83 86.48 24Nd1.85Ce0.15CuO4 41.51 80.71 24Standard bond energies C-H bond 99 1 C-C bond 83 1
C-N bond 73 1Hydrogen bonding in water ~5 1
Van der Waals bonding ~1 1
Covalency and metallicity of TMCs and some standard bonding
energies.
A. Chainani et al. PRB 87, 045108 (2013)
HAXPES results from our group :Zhang-Rice doublet state in NiO PRL 100 206401(2008)
Changes across successive first-order transitions in the Magneli compound Ti4O7 PRL 104,106401(2010)
Paramagentic insulator to Anti-ferromagnetic metal transition in CrN PRL 104,236404(2010)
Mixed Valency in a quantum critical f-electron system YbAlB4 PRL 104,247401(2010)
Recoil effects of core and valence photoelectron in solidsY. Takata, et al., PRL101, 137601(2008)
Recoil effects in PES:C 1s core level spectra of graphite
Y. Takata et al., PRB 75, 233404 (2007)
285.5 285.0 284.5 284.0
Pn
oto
ele
ctro
n In
ten
sity
Binding Energy (eV)
KE dependence at normal emission
h=7940eVE=120meV)
h=5950eV(E=120meV)
h=870eVE=100meV)
★ not observed in Au ★ not due to semimetallic
character ★ not due to bulk vs
surface but due to recoil effect !
Recoil effects in core level spectra of other light elements, such as
(Be, B, Al)
Recoil effects in valence band (Fermi-edge) of Al@ 7.94keV
Y. Takata, Y. Kayanuma et al.,Phys. Rev. Lett.101, 137601(2008)
Inte
nsit
y (a
rb. u
nits
)
1.0 0.5 0.0 -0.5 -1.0Binding Energy (eV)
h = 7.94 keVE = 120 meVT = 20 K
AuAl
M(Au): 197 (m/M)xE: 22meV
M(Al): 27.0 (m/M)xE: 160meVE=119meV 2p:115meV
Gaussian width Au:124meV Al: 160meV
Theory by Y. Kayanuma, S. Tanaka and S. OshimaY. Takata, Y. Kayanuma et al.,Phys. Rev. Lett.101, 137601(2008)
isotropic Debye model
04/11/23 61
04/11/23 62
04/11/23 63
A X Gray et al, Nature Materials, 11, 957(2012)
Bulk electronic structure of Ga1-xMnxAs
04/11/23 64
Bulk electronic structure of Ga1-xMnxAs
A X Gray et al, Nature Materials, 11, 957(2012)
04/11/23 65
Future ProspectsFuture Prospects
★ Improvement of energy resolution to ~10 meV
★ Angle resolved measurements
VB mapping
Photoelectron diffraction
★ Polarization dependence
★ Atoms and molecules
non-dipole effects
★ Dynamics using time resolved HAXPES
★Application to high vapor pressure systems
Liquids/Wet samples/Gels
Gray et al
Ueda et al
Simon et alCastro et al
04/11/23 66
Y Takashima et alNature Commun. Dec 2012DOI:10.1038/ncomms2280
04/11/23 67
Irene Chen et al.,Advanced Functional Materials22, 2535(2012)
04/11/23 68
HAXPES has become a valuable tool !SPring-8 (6 beamlines, not dedicated)ESRFBNL BESSY IISOLEILPETRA III ERL ?…..
04/11/23 69
International WS to Conferences on HAXPES
1st in 2003 @ ESRF by Zegenhagen
2nd in 2006@ SPring-8 by Kobayashi and Suga
3rd in 2009 @ NSLS by Woicik and Fadley
4th in 2011 @ HASYLAB by Drube
5th in 2013 @ Uppsala by Svensson and Martensson
Thank you very muchfor your attention
04/11/23 70
Science 287, 1019 (2000)Mn:GaAs
04/11/23 71
04/11/23 72
Ti 2p HX-PES
M. Taguchi et al, PRL 104, 106401 (2010)04/11/23 73
*-Udc|
2p53d0
-Udc|
*
3d1L
3d1C
3d0
2p53d1L
2p53d1C
CT| g › | f ›
HT phase
04/11/23 74
Ti4+ cluster（ V* =0 ）
Ti 3+
Ti3+
Ti4+
LT phase
04/11/23 75
04/11/23 76
Ti4+ cluster（ V* =0.3 eV ）
Ti 3+
Remnant ofCoherent states
IT phase
04/11/23 77
04/11/23 78
SUMMARYRuthenates with and without orbital order exhibit Mott-Hubbard type band-width controlled metal-insulator transitions
The Magneli phase compound Ti4O7 has an anomalous intermediatephase sandwiched between a Fermi liquid and charge ordered insulator
Equivalence of screening due to coherent states and non-local screening
Accurate Valence determination in d and f electron systems
04/11/23 79
Semiconductors : HfO2:SiO2 (K. Kobayashi et al) SiO2/Si(100) (Y. Takata et al), GaAs (C. Dallera et al), Cr : GaN( J.J. Kim et al),
Si (F. Offi et al), In2O3 (A. Walsh et al), etc.
Elements : Co, Cu, Ag, Ni, etc. (M.Sacchi et al, G. Panaccione et al, O. Karis et al)
f-electron systems : Ce systems (L. Braicovich et al, P. Fevre et al, M. Matsunami et al)
Yb Mixed valence (H. Sato et al, A. Yamasaki et al), Yb Kondo (L. Moreschini et al)
Titanates : XSW partial DOS ( J Woicik et al) ; Resonant Auger (J. Danger et al )
Vanadates : Mott-Hubbard transition (N. Kamakura et al, M. Taguchi et al, G. Panaccione et al, J.
Woicik et al )
Cobaltates : charge order (A. Chainani et al)
Manganites : doping dependence(K. Horiba et al), bilayer (F. Offi et al , S. de Jong et al)
T-dependence (H. Tanaka et al, F. Offi et al, S. Ueda et al,)
Cuprates : hole and electron doping (M. Taguchi et al, G. Panaccione et al, K. Maiti et al)
Iron Pnictides : LaFePO(Y Kamihara et al) ; BaFe2As2 (S. de Jong et al)
Nickelates : NiO (J. Woicik et al, M. Taguchi et al)
Importance of s-states in a metallic oxide : PbO2 (D. J. Payne et al)
Intermetallics : Huesler alloys ( C. Felser et al)
Ruthenate complexes : role of intermolecular interactions ( S Svensson et al)
Multilayers : Ni/Cu (Holmstrom et al)
Oxide Multilayers : LaAlO3/SrTiO3 (M. Sing et al) ; LaVO3/LaAlO3 (M. Takizawa et al)
04/11/23 80
HAXPES has become a standard tool !SPring-8 (6 beamlines, not dedicated)ESRFNSLS BESSY IISOLEILAPS PETRA III ALS?MAX-IV?
…..
04/11/23 81
International WS on HAXPES
1st in 2003 @ ESRF by Zegenhagen
2nd in 2006@ SPring-8 by Kobayashi and Suga
3rd in 2009 @ NSLS by Woicik and Fadley
4th in 2011 @ HASYLAB by Drube
5th in 2013 @ Uppsala by Svensson and Martensson
04/11/23 82
Future ProspectsFuture Prospects
★ Improvement of energy resolution to ~20 meV
★ Angle resolved measurements
VB mapping
Photoelectron diffraction
★ Polarization dependence
★ Application to high vapor pressure systems
Liquids/Wet samples
★ Atoms and molecules
non-dipole effects
Recoil & Dynamics
Fadley, Papp et al
Ueda et al
Simon et alCastro et al
Thank You very much
04/11/23 83
Comparison with Nb:STO(SrTiO3)
Y. Ishida et al PRL 100, 056401 (2008)
04/11/23 84
Y. Ishida et alPRL 100,056401 (2008)
04/11/23 85
04/11/23 86
04/11/23 87
Y Aiura et al.Surface Science515, 61 (2002)
04/11/23 88
n-type SrTiO3-
J. Chang et al PRB81,235109(2010)
04/11/23 89
Nature 469, 189 (2011)
04/11/23 90
O K-edge XAS
04/11/23 91
O K-edge Resonant PES
04/11/23 92
Constant initial state spectra across the O K-edge
04/11/23 93
Partial density of states near EF
Y. Ishida et al PRL 100, 056401 (2008)04/11/23 94
Ti 2p-3d Resonant PES
Coherent +Incoherent
feature
T. Ohtsuki et alPRL 106,047602(2011)
04/11/23 95
Cu 2p XPS (experiments)
M. A. van Veenendaal and G. A. Sawatzky, Phys. Rev. B 49, 3473 (1994)K. Okada and A. Kotani, J. Electron Spectrosc. Relat. Phenom. 86, 119 (1997).
K. Karlsson, O. Gunnarsson andO. Jepsen, Phys. Rev. Lett. 82, 3528 (1999) ; A. Koitzsch et al., Phys. Rev. B 66, 024519 (2002).
O 1s XPS (Experiment)
Peak shift
NCCO LCO
0.25 eV
LCO LSCO
0.2 eV
Peak shift is rather small as compared with optical gap （ 1.0 eV ）
O 1s XAS
O 1s level
UHB
UHB
LSCO
NCCO
C. T. Chen et al. Phys. Rev. Lett 66, 104(1991) ; M. Romberg et al. Phys. Rev. B 43, 333(1991)
T. Fukumura et alNew Journal of Physics10, 055018 (2008)
04/11/23 99
Recoil effects in valence band (Fermi-edge) of Al@ 880eV
1.0 0.5 0.0 -0.5 -1.0Binding Energy (eV)
Inte
nsit
y (a
rb. u
nits
)
h = 880 eVE = 120 meVT = 50 K
AuAl
Inte
nsit
y (a
rb. u
nits
)
150 100 50 0 -50 -100 -150Binding Energy (meV)
h = 880 eVE = 120 meVT = 50 K
AuAl
M(Au): 197 (m/M)xE: 2meV
M(Al): 27.0 (m/M)xE: 18meVE=12meV Gaussian width Au:118meV Al: 140meV
Our Experiments :Epitaxial films grown by pulsed laser deposition
Characterization :Structure and ferromagnetism
X-ray Absorption Spectroscopy(XAS)Resonant photoemission(PES) @ BL17E ~230 meV at Ti L-edge
Hard X-ray PES @ BL 29E ~250 meV at h = 8 KeV
04/11/23 101
XRD RHEEDSamples : PLD grown films characterized by x-ray diffraction RHEED oscillationRHEED pattern
04/11/23 102
New Journal of Physics10, 055018 (2008)
04/11/23 103
0.8 B/Co
T. Fukumura et alNew Journal of Physics10, 055018 (2008)
04/11/23 104
Recoil effects in photoelectron emissionTheory by Y. Kayanuma & S. Tanaka (PRB 75, 233404 (2007) )
For an atom in free space E=(m/M)E E:recoil energy M: atomic mass m: electron mass E: kinetic energy
For C atom at 8 keV m/M=1/22000 E=0.36 eV
In graphite E is absorbed by the phonon bath. Excitation of phonons
Mössbauer effect in -ray emission
Theoretical calculation: Debye model
Normal emission: hD=75meV
Emission Angle Dependence
e-
285.5 285.0 284.5 284.0
normal (85deg)
(a) Experiment
GraphiteC 1sh=7940eV
Binding Energy (eV)
grazing (30deg)
1.0 0.5 0.0 -0.5
out-of-plane(bending)
in-plane(stretching)
Recoil Energy (eV)
(b) Theory
Normal emission: hD=75meVGrazing emission: hD=150meV
Recoil effects in PES reflect phonon dynamics!
Comparison of recoil effects in graphiteM. Vos, et al., PRB 78, 024301(2008)
photoelectron emission
electron scattering
neutron scattering
287 286 285 284 283 282
B-doped Diamond
HOPG
C 1sR.T.
No
rma
kize
d I
nte
nsi
ty
Binding Energy (eV)
5.95keV 7.94keV
Comparison between Diamond & Graphite
LDA & (LDA + DMFT) of Hg2Ru2O7Importance of multi-orbital correlations
negligible influence of spin-orbit coupling
24
L. Craco et al, PRB 79, 075125 (2009)
S. Baidya et al, PRB 86, 125117 (2012)
A. Chainani et al. PRB 87, 045108 (2013)
(3~4
04/11/23 113
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
Estimation of IMFP value
N(z)=N0exp(-z/)
(4keV)=5nm in LBMO
surface layer contribution
layer distance0.4nm
=1nm: 33%=5nm: 8%=10nm: 4%higher KE larger
H. Tanaka et al.,
Phys. Rev. B 73, 094403 (2006)
Be 1s core level of polycrystalline Be
Photo
ele
ctro
n Inte
nsi
ty
114 113 112 111Binding Energy (eV)
BeBe 1s @ 20KE=110meV (SX) 125meV(HX)
h=880eV
h=5950eV
h=7940eVSurface
h=5950eV
h=7940eV
Atomic weight: 9.0E(5950eV)=330meV (m/M)xE: 355meVE(7940eV)=440meV (m/M)xE: 475meVSurface
feature
B 1s core level of MgB2
Photo
ele
ctro
n Inte
nsi
ty
189 188 187 186Binding Energy (eV)
MgB2
B 1s @20KE=110meV (SX) 125meV(HX)
h=880eV
h=7940eV
h=5950eV
a bundle of needle crystals supplied by H. Kitoh @NIMS
Atomic weight: 10.8E(5950eV)=240meV (m/M)xE: 290meVE(7940eV)=340meV (m/M)xE: 390meV
Al 2p core level of Al thin filmP
hoto
elec
tron
Inte
nsity
74.5 74.0 73.5 73.0 72.5 72.0Binding Energy (eV)
AlAl 2p @ 20KE=110meV (SX) 125meV(HX)
h=880eV
h=7940eV
h=5950eV
Atomic weight: 27.0E(5950eV)=90meV (m/M)xE: 120meVE(7940eV)=115meV (m/M)xE: 160meV
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XMCD
synthesis and annealing in oxygen
K. Mamiya, T. Koide,A. Fujimori et al, APL 89, 062506
(2006)
04/11/23 118
Early spectroscopy : Controversy
PRL 90, 017401(2003)04/11/23 119
Ferromagnetism is due to Co clusterspostannealing in Vacuum
J. Y. Kim et al PRL 90, 017401(2003)04/11/23 120
What is different ?
Reducing atmosphere : Co clusters
versus
Oxidizing atmosphere : Co2+ Intrinsic ferromagnetism
04/11/23 121
EXAFS of Co:TiO2
04/11/23 122
Ti 2p and O 1s core levels
04/11/23 123
A. Chainani et al. PRB 87, 045108 (2013)
(3~4
V 1s core level PES of V2O3
• PM (V ∗ = 0.75)
• T = 250 K
• AFI (V ∗ = 0) phases.
• T = 90 K
N. Kamakura et al.Europhysics Letters 68, 557(2004)
charge neutrality condition : Co2+ + VO 2− + 2Ti 4+ Co 2+ + 2Ti 3+
(VO is oxygen vacancy)
Surface Science, 601, 5034
(2007)
New.J.Phys. 10, 055018
(2008)04/11/23 127
04/11/23 128
Need to account for X-ray photoelectron diffraction intensity and density of states effects
A X Gray et al, Nature Materials, 10, 759(2011)
