Photoelectron Spectroscopy: Bulk and Surface Electronic Structures

389 Pages·2014·12.94 MB·English

by  Shigemasa Suga

Springer Series in Optical Sciences 176
Shigemasa Suga
Akira Sekiyama
Photoelectron
Spectroscopy
Bulk and Surface Electronic Structures
Springer Series in Optical Sciences
Volume 176
Founded by
H. K. V. Lotsch
Editor-in-Chief
W. T. Rhodes
Editorial Board
Ali Adibi, Atlanta
Toshimitsu Asakura, Sapporo
Theodor W. Hänsch, Garching
Takeshi Kamiya, Tokyo
Ferenc Krausz, Garching
Bo A. J. Monemar, Linköping
Herbert Venghaus, Berlin
Horst Weber, Berlin
Harald Weinfurter, München
For furthervolumes:
http://www.springer.com/series/624
Springer Series in Optical Sciences
TheSpringerSeriesinOpticalSciences,undertheleadershipofEditor-in-ChiefWilliamT.Rhodes,
GeorgiaInstituteofTechnology,USA,providesanexpandingselectionofresearchmonographsinall
majorareasofoptics:lasersandquantumoptics,ultrafastphenomena,opticalspectroscopytechniques,
optoelectronics, quantum information, information optics, applied laser technology, industrial appli-
cations,andothertopicsofcontemporaryinterest.
Withthisbroadcoverageoftopics,theseriesisofusetoallresearchscientistsandengineerswhoneed
up-to-datereferencebooks.
Theeditorsencourageprospectiveauthorstocorrespondwiththeminadvanceofsubmittingaman-
uscript.SubmissionofmanuscriptsshouldbemadetotheEditor-in-ChieforoneoftheEditors.Seealso
www.springer.com/series/624
Editor-in-Chief
WilliamT.Rhodes
SchoolofElectricalandComputerEngineering
GeorgiaInstituteofTechnology
Atlanta,GA30332-0250
USA
e-mail:[email protected]
EditorialBoard
AliAdibi BoA.J.Monemar
SchoolofElectricalandComputerEngineering DepartmentofPhysicsandMeasurementTechnology
GeorgiaInstituteofTechnology MaterialsScienceDivision
Atlanta,GA30332-0250 LinköpingUniversity
USA 58183Linköping,Sweden
e-mail:[email protected] e-mail:[email protected]
ToshimitsuAsakura HerbertVenghaus
FacultyofEngineering FraunhoferInstitutfürNachrichtentechnik
Hokkai-GakuenUniversity Heinrich-Hertz-Institut
1-1,Minami-26,Nishi11,Chuo-ku Einsteinufer37
Sapporo,Hokkaido064-0926,Japan 10587Berlin,Germany
e-mail:[email protected] e-mail:[email protected]
TheodorW.Hänsch HorstWeber
Max-Planck-InstitutfürQuantenoptik OptischesInstitut
Hans-Kopfermann-Straße1 TechnischeUniversitätBerlin
85748Garching,Germany Straßedes17.Juni135
e-mail:[email protected] 10623Berlin,Germany
e-mail:[email protected]
TakeshiKamiya
MinistryofEducation,Culture,Sports HaraldWeinfurter
ScienceandTechnology SektionPhysik
NationalInstitutionforAcademicDegrees Ludwig-Maximilians-UniversitätMünchen
3-29-1OtsukaBunkyo-ku Schellingstraße4/III
Tokyo112-0012,Japan 80799Munchen,Germany
e-mail:[email protected] e-mail:[email protected]
FerencKrausz
Ludwig-Maximilians-UniversitätMünchen
LehrstuhlfürExperimentellePhysik
AmCoulombwall1
85748Garching,Germanyand
Max-Planck-InstitutfürQuantenoptik
Hans-Kopfermann-Straße1
85748Garching,Germany
e-mail:[email protected]
Shigemasa Suga Akira Sekiyama
•
Photoelectron Spectroscopy
Bulk and Surface Electronic Structures
123
Shigemasa Suga Akira Sekiyama
Institute of Scientific and Industrial Graduate School of Engineering
Research Science
Osaka University Osaka University
Osaka Osaka
Japan Japan
ISSN 0342-4111 ISSN 1556-1534 (electronic)
ISBN 978-3-642-37529-3 ISBN 978-3-642-37530-9 (eBook)
DOI 10.1007/978-3-642-37530-9
SpringerHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2013937610
(cid:2)Springer-VerlagBerlinHeidelberg2014
Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof
the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor
informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodology now known or hereafter developed. Exempted from this legal reservation are brief
excerpts in connection with reviews or scholarly analysis or material supplied specifically for the
purposeofbeingenteredandexecutedonacomputersystem,forexclusiveusebythepurchaserofthe
work. Duplication of this publication or parts thereof is permitted only under the provisions of
theCopyright Law of the Publisher’s location, in its current version, and permission for use must
always be obtained from Springer. Permissions for use may be obtained through RightsLink at the
CopyrightClearanceCenter.ViolationsareliabletoprosecutionundertherespectiveCopyrightLaw.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt
fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.
While the advice and information in this book are believed to be true and accurate at the date of
publication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityfor
anyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,with
respecttothematerialcontainedherein.
Printedonacid-freepaper
SpringerispartofSpringerScience+BusinessMedia(www.springer.com)
Preface
The phenomenon of photoelectron emission was found more than a century ago
andyieldedtheconceptofphotons.Therelationbetweenthephotonenergiesand
the kinetic energies of photoelectrons was soon clarified. The usefulness of pho-
toelectronspectroscopy(PES)formaterialsscienceswaswidelyrecognizedinthe
last century. Electronic structures of gases and solids were mostly studied at low
photon energies and chemical analyses were mainly performed in the X-ray
region. Besides the development of high performance electron analyzers, light
sourceshaveinparallelbeenintensivelyimprovedtilldate.Theuseofsynchrotron
radiation has promoted the photoelectron spectroscopy since *1975 due to the
tunabilityofphotonenergies.Thedevelopmentofundulatorlightsourcesenabled
the high energy resolution photoelectron spectroscopy even in the regions of soft
andhardX-rays.Now,synchrotronradiationcanprovidephotonswithenergy(hm)
resolutions less than a few meV below 10 eV, 40 meV around 800 eV, and less
than 300 leV at 14 keV by use of good monochromators. Meanwhile, the reso-
lutionB1meVcanbeachievedinlaboratoriesbyuseofverylowenergy(*7eV)
quasi-CW, high-repetition lasers as well as high resolution rare gas (Xe, Kr, Ar)
lamps.
Byutilizingtheangleresolvingpoweroftheelectronenergyanalyzer,theangle
resolved photoelectron spectroscopy (ARPES) became very popular to probe the
band dispersions of solids as well as the fermi surface topology in metals. In
stronglycorrelatedelectronsystems,wherethesurfaceelectronicstructuresaswell
as surface band dispersions are often noticeably different from those of the bulk
electronic structures, the high energy photoelectron spectroscopy with high bulk
sensitivity and enough energy and momentum resolutions is now extensively
performed. Since the inelastic mean free path of photoelectrons becomes again
increasedinsomematerialsbelowthekineticenergiesofafeweV,extremelyhigh
resolution photoelectron spectroscopy is under development below hm *10 eV.
For a complete understanding of electronic structures of strongly correlated elec-
tronsystems,studiesinwidephotonenergiesintherangeof10keVdowntoafew
eV will be highly desired. By utilizing the high brilliance of the synchrotron
radiation, studies of micro- and nano-materials are progressing rapidly. The
v
vi Preface
scanningphotoelectronmicroscopyandthephotoelectronemissionmicroscopyare
suchexamples.Inaddition,spinpolarizedmeasurementsarewidelyusedtostudy
the spin states.
Complementary techniques to probe materials electronic structures are also
under intensive development. For example, absorption and reflectivity spectros-
copy as well as the resonance inelastic X-ray scattering are very powerful tech-
niques with high bulk sensitivity. Inverse photoemission spectroscopy is a useful
tool to probe the unoccupied electronic states. On the other hand, photoelectron
diffraction can provide the structural information down to sub nm range. The
scanningtunnelingspectroscopybyuseofscanningtunnelingmicroscopecanalso
probe the occupied and unoccupied electronic states with extremely high spatial
resolution down to the atomic resolution. By means of the Fourier transform, the
information in the momentum space can also be obtained. Thus we intended to
include up-to-date achievements in photoelectron spectroscopy and frontiers of
some typical complementary techniques in this book.
Osaka Shigemasa Suga
Akira Sekiyama
Acknowledgments
The photoelectron spectroscopy with use of such a bright light source as syn-
chrotron radiation has already a history of more than four decades. One of the
authors S. S. has first experienced synchrotron radiation photoelectron spectros-
copyin1975atDESYwithF.J.Himpsel.TheinitialinterestofS.S.inthisfield
wasstimulatedbyM.CardonaofMax-Planck-InstitutefürFestkörperforschungin
StuttgartinthelaststageofhisstayinGermanybetween1973and1976.S.S.was
then engaged in the instrumentation, spectroscopy, and materials’ sciences in the
synchrotronradiationlaboratoryoftheInstituteforSolidStatePhysics(ISSP),The
UniversityofTokyo,withadedicated synchrotronlight source, SOR-RING (0.38
GeV), where he was responsible for the national use of this facility over 13 years
togetherwithH.KanzakiandT.Ishii.TherehecooperatedwithM.Taniguchiand
S. Shin in photoelectron spectroscopy. He also collaborated with A. Fujimori on
XPSand S.-J. Oh on resonance photoelectronspectroscopy. He was alsoengaged
inVUV-IPESandX-BISwithH.NamatameandS.Ogawa.Duringthisperiodhe
also joined spin polarized electron experiments at BESSY-I and KFA, Jülich in
collaboration with J. Kirschner. He also collaborated with A. Kakizaki, K. Soda,
M. Fujisawa, and T. Kinoshita to construct two beam lines of the ISSP at Photon
Factory (2.5 GeV) in Tsukuba.
He then moved to Osaka University in 1989 to join the SPring-8 (8 GeV)
project as an active outside user. He devoted the full potential of his old and new
laboratories to the construction of the first soft X-ray beam line, BL25SU, of
SPring-8withatwinhelicalundulator(designedbyH.Kitamura)togetherwithH.
Daimon, S. Imada, and Y. Saitoh. Excellent performance of the soft X-ray
monochromatorequippedwithvariedlinespacingplanegratingswasconfirmedat
BL25SU in 2000 by the author’s group. Till the full commissioning of this new
beam line with three different experimental stations (soft X-ray photoelectron
spectroscopy, soft X-ray absorption magnetic circular dichroism, and photoelec-
tron diffraction with two-dimensional electron analyzer) in 1998, he continued
such experiments at Photon Factory. He met with the other author A. S. in 1995,
who was a Ph.D. student under supervision of A. Fujimori in The University of
Tokyo. A.S. partly collaborated with S. S.on the experimentsat Photon Factory,
andthenmovedtoOsakaUniversityaftertakinghisPh.D.degreetojoinS.S.lab.
Both authors did extensive PES studies on rare earth compounds. During this
vii
viii Acknowledgments
period,theybecameacquaintedwithP.Baltzerwithwhomtheydiscussedquitea
lot on electron analyzers and the future of bulk sensitive photoelectron spectros-
copy. It must be mentioned here that four more soft X-ray beam lines were later
constructed up to now in SPring-8, demonstrating that an 8 GeV storage ring is
very useful for soft X-ray spectroscopy.
Through various research collaborations making use of this high performance
soft X-ray BL25SU, the authors profited immensely from discussions with
J. W. Allen, D. Vollhardt, V. I. Anisimov, R. Claessen, M. Sing, G. Güntherodt,
J. Osterwalder, J.-S. Kang, and W. Kuch. In our recent activity in the hard X-ray
region,theauthorsaremuchobligedtoT.Ishikawa.S.S.isalsomuchobligedto
C. M. Schneider and L. Plucinski for collaboration in the field of extremely low
energy photoelectron spectroscopy. The authors would like to thank all of these
peopleforfruitfulcollaborationsanddiscussions.Thisbookhasbenefittedquitea
lot from continuous cooperation and discussions with many foreign and domestic
friends as well as colleagues in the field of synchrotron radiation spectroscopy.
Thecontentofthisbookisbasedonthelectures,whichS.S.gavefrom1980in
the Graduate School of Applied Physics, The University of Tokyo and later from
1989 in the Graduate School of Engineering Science, Osaka University. It is also
based on the lectures given by A. S. from 2010 in the latter graduate school. The
very recent studiesperformedtogetherwith A.Yamasaki, H.Fujiwara, and many
other students in the graduate school are included in this book and the authors
acknowledge them all.
Over a long period of his life, S. S. acknowledges his wife Sachiha for her
patience and appreciation of his hard scientific job while taking care of their four
children.A.S.acknowledgeshiswifeHarukoforsupportinghisresearchestilllate
at night while taking care of two children. S. S. is much obliged to the Japan
Society for Promotion of Science for twice supporting the Japan–Germany
research collaborations and the Ministry of Education, Culture, Sports, Science
and Technology, MEXT, Japan, for financial supports through COE, 21COE, and
Grant-in-AidsforCreativeScientificResearch(15GS0213).A.S.thankstheJapan
Society forpromotionofscience forfinancialsupportthroughGlobalCOE(G10)
and scientific research on innovative areas ‘‘Heavy Electrons’’ (20102003). S. S.
also thanks the Helmholtz Association and the Alexander von Humboldt Foun-
dation for supporting the Japan–Germany research collaborations.
The authors are much obliged to A. Yamasaki of Konan University, Japan,
M. Sing of University of Würzburg, Germany, K. Sakamoto of Chiba University,
and T Okuda of Hiroshima University Japan, for their careful reading of the first
manuscript and many useful comments for further improvement. The stimulating
discussion with A. Winkelmann of the Max-Planck Institute for Microstructure
Physics, Germany, is highly acknowledged. This book would not have been
completed withoutthe patience andcontinuous encouragementofC. Ascheron of
Springer-Verlag.
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Three-Step Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Valence-Band Photoexcitation Process for Non-interacting
Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 Valence-Band Photoexcitation Process for Strongly
Correlated Electron Systems . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 Core-Level Photoemission Process for Strongly
Correlated Electron Systems . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5 Matrix Element Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.6 Theoretical Models to Describe the Spectra of Strongly
Correlated Electron Systems . . . . . . . . . . . . . . . . . . . . . . . . 21
2.6.1 Single Impurity Anderson Model . . . . . . . . . . . . . . . 24
2.6.2 Cluster Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.6.3 Hubbard Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.6.4 Dynamical Mean Field Theory. . . . . . . . . . . . . . . . . 28
2.6.5 New Directions and Some Remarks . . . . . . . . . . . . . 29
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3 Instrumentation and Methodology. . . . . . . . . . . . . . . . . . . . . . . . 33
3.1 Synchrotron Radiation and Undulator Radiation. . . . . . . . . . . 33
3.2 Principle of Grating and Crystal Monochromators . . . . . . . . . 37
3.2.1 Grating Monochromators. . . . . . . . . . . . . . . . . . . . . 38
3.2.2 Crystal Monochromators. . . . . . . . . . . . . . . . . . . . . 42
3.2.3 Focusing Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3 Examples of Light Sources . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3.1 High Resolution Vacuum Ultraviolet Synchrotron
Radiation Beam Lines. . . . . . . . . . . . . . . . . . . . . . . 45
3.3.2 High Resolution Soft X-ray Beam Lines. . . . . . . . . . 49
3.3.3 High Resolution Hard X-ray Beam Lines . . . . . . . . . 52
3.3.4 Laboratory Vacuum Ultraviolet Sources . . . . . . . . . . 54
ix