Table Of Contentspringer series in surface sciences
49
•
springer series in surface sciences
SeriesEditors:G.Ertl,H.Lu¨thandD.L.Mills
Thisseriescoversthewholespectrumofsurfacesciences,includingstructureanddynamics
ofcleanandadsorbate-coveredsurfaces,thinfilms,basicsurfaceeffects,analyticalmethods
andalsothephysicsandchemistryofinterfaces.Writtenbyleadingresearchersinthefield,
thebooksareintendedprimarilyforresearchersinacademiaandindustryandforgraduate
students.
PleaseviewavailabletitlesinSpringerSeriesinSurfaceSciences
onserieshomepagehttp://www.sprin• ger.com/series/409
Siegfried Hofmann
Auger- and X-Ray
Photoelectron
Spectroscopy
•
in Materials Science
A User-Oriented Guide
With262Figures
123
ProfessorDr. SiegfriedHofmann
Max-Planck-Institute for Intelligent Systems
(formerly Max-Planck-Institute for Metals R esearch)
Heisenbergstrasse 3, 70569 Stuttgart, Germany
[email protected] or [email protected]
SeriesEditors:
ProfessorDr.GerhardErtl
Fritz-Haber-InstitutederMax-Planck-Gesellschaft,Faradayweg4–6,
14195Berlin,Germany
ProfessorDr.HansLu¨th
Institutfu¨rSchicht-undIonentechnik
ForschungszentrumJu¨lichGmbH,
52425Ju¨lich,Germany
ProfessorDouglasL.Mills,Ph.D.
DepartmentofPhysics,UniversityofCalifornia,•
Irvine,CA92717,USA
SpringerSeriesinSurfaceSciences ISSN0931-5195
ISBN978-3-642-27380-3 ISBN978-3-642-27381-0 (eBook)
DOI10.1007/978-3-642-27381-0
Springer Heidelberg New York Dordrecht London
Library of Congress Control Number: 2012942909
© Springer-Verlag Berlin Heidelberg 2013
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Dedicatedto theMemoryof myFather
Georg AdamHofmann,
MuRllermeisterin Dietenhofen/MoosmuRhle
(cid:2)13. April1901(cid:2)15.December 1969
•
Foreword
Surface chemical analysis is used extensively for a wide range of purposes in
scienceandtechnology.Technologically,surfaceandinterfacepropertiesarecrucial
for the fabrication and performance of a wide range of advanced materials (e.g.,
ceramics, composites,alloys, polymers,superconductors,diamond-likethin films,
and biomaterials), semiconductor devices, optoelectronic materials, high-density
magnetic-storage media, sensors, thin films, and coatings. Surface or interface
integrityiscriticalformanypropertiesorprocesses,suchastheelectricalbehavior
of a semiconductor device, the wear or corrosion of an automobile part, or the
degradation of an implant material in the human body. Surface analysis is used
in these applications for failure analysis in manufacturing or of a component in
its service environment as well as for monitoring steps in product fabrication or
processdevelopment.Thesurfacecompositionmayberequiredforproductquality
controlor may be usefully correlated with specific material properties, processes,
or phenomena (e.g., corrosion, adhesion, lubrication, wear, segregation of bulk
impurities to interfaces, and diffusion, among many others) so that improvements
canbedeveloped.Surfaceandinterfacepropertiesarealsocriticalinmanyareasof
public concern ranging from new sources of energy (e.g., photovoltaics and fuel
cells) to defence systems (e.g., sensors and stability of high-power laser optical
components)andhealthandenvironmentalproblems(e.g.,particulatepollutantsin
theatmosphereandthestabilityofstorednuclearwaste).Twoofthemostcommonly
usedsurfaceanalysistechniquesareAuger-electronspectroscopy(AES)andX-ray
photoelectronspectroscopy(XPS).Thesetechniquesareutilizedindifferentmodes
toobtaininformationonthenear-surfacecompositionand,inconjunctionwithion
sputteringorothermethodstoremovesurfacelayers,todeterminethecomposition
ofthematerialasafunctionofdepthfromtheoriginalsurface.Formanyadvanced
materials (e.g., semiconductor devices, magnetic storage media, and new classes
of nanostructures and nanomaterials), the materials are fabricated with critical
dimensions on the nanometer scale and there is little distinction between surface,
bulk, thin film, and interface properties. A growing need in these applications is
to determine composition as a function of position, particularly in the vicinity
of surfaces and interfaces for materials that may have complex morphologies.
vii
viii Foreword
CommercialinstrumentsforAESandXPSbecameavailablesomefourdecadesago,
andtheinstrumentalcapabilities(e.g.,insensitivity,spatialresolution,andimaging)
have improved dramatically over the years. While the early instruments were
controlledmanuallyandinformationwasobtainedwithanaloguesystems,modern
instruments are controlled by computers with advanced software for instrument
setup, operation, data acquisition, and data analysis. The principles of AES and
XPS are relativelyeasy to understand,but it can neverthelessbe difficultto select
instrumentaloperatingconditionstoobtainthedesiredinformationasefficientlyas
possible.Manyartifactscanariseindataacquisitionandtherecanbecomplexities
intheinterpretationandanalysisofacquireddata,particularlyforinhomogeneous
specimens.ThiswelcomebookbySiegfriedHofmannprovidesextensiveguidance
to novice as well as experienced surface analysts. Throughout his distinguished
career, Hofmann has made numerous significant contributions to applied surface,
rangingfromthedevelopmentofnewmethodstoapplicationsinmaterialsscience.
Herecognizedearlytheimportanceofsurfaces,interfaces,andthinfilmsinmany
fields, and developed analytical methods of increasing sophistication and detail
to obtain quantitative information for the solution of a wide range of practical
problems. Hofmann has distilled his extensive knowledge and experience into an
extremelyusefulbook.Hofmann’sbookprovidesa comprehensiveaccountof the
basic principles of AES and XPS (Chaps. 1 and 3), the available instrumentation
(Chap. 2), and the many factorsthat need to be consideredin surface analyses by
these techniques.The two longestchapters, Chap.4 on quantitativeanalysis (data
evaluation)” and Chap. 7 on quantitative compositional depth profiling, contain a
cleardescriptionoffactorsaffectingthemeasuredsignalintensitiesaswellashow
the intensities are modified by specimen inhomogeneities. Worked examples are
provided with typical data to illustrate concepts and the application of different
analytical approaches. Other chapters give guidance on optimizing experimental
conditions(Chap.5),onoptimizingcertaintyandthedetectionlimit(Chap.6),and
on developing an analytical strategy for AES and XPS measurements (Chap. 8).
Finally,Chap.9givesexamplesoftypicalAESandXPSapplicationsinmaterials
science. While AES and XPS are extensively used for qualitative purposes, this
bookprovidesthebestandclearestaccountIamawareofonhowtomakedifferent
typesofquantitativeAESandXPSanalysesforvarioustypesofsamples.Readers
will also welcome the author’s focus on using the instruments as effectively and
efficiently as possible and on solving different types of practical problems. Most
AESandXPSanalystswillfindthisbooktobeavaluableresource.Irecommendit
strongly.
CedricJ.Powell
Preface
The aim of this book is mainly to help the practical analyst in his daily work
on a rather basic level. Furthermore, it should serve as a guide for students
working for their master’s or Ph.D. thesis in materials science by teaching them
about capabilities and limitations of applied surface analysis using AES and
XPS in their special field. The reader may ask: why another book on a topic
that is already covered by excellent books such as Briggs and Seah (1990) [1],
Briggs and Grant [2], and Watts and Wolstenhome [3]. The answer is manifold:
Book[1] isstillexcellentbutoutdatedinsomespecialalthoughimportantaspects
of quantitative analysis or depth profiling; book [2], thought as a replacement of
[1] after 13 years, in many aspects is too much detailed and theoretically based
for practical applications, a book aimed at the advanced spectroscopist. Book [3]
is highly recommended as an introduction for the beginner but as such lacks
the quantitative information and data needed for the practical researcher in daily
work. In short, the author’s intention is to provide a compendium that fulfills the
gap between [2] and [3]. In addition, the above argument for [2] may hold here
too, since at least a few topics were introduced only in recent years, such as the
surface excitation parameter (SEP) or the backscattering correction factor (BCF).
Furthermore, I adopt the point of view already mentioned by Rene´ Descartes in
1637 (p. 11 of Ref. [4]): “...there is often less perfection in works composed of
severalparts,andmadebythehandsofavarietyofcontributors,thaninthoseone
which only one person has worked on ....”. After having established the surface
and interface analysis group in the Max Planck Institute on Metals Research in
Stuttgart,theauthorhasworkedmorethan30yearsinapplicationofAESandXPS
to Materials Science. This seems to be an advantage at first sight, but it bears an
inevitable disadvantage:personallyunique experienceleaves everybodysomehow
biased about the importance and the treatment of specific topics. Therefore, the
bookappearslikeahomunculuspictureinpsychology,wherethesizeofanorgan
is displayed according to the volume the brain needs for its operation. Thus,
I have to apologize that the contents may appear somehow imbalanced to many
colleagues. For example, sputter depth profiling is highly emphasized, as are the
practicalissuesofquantification,signal-to-noiseanddetectionlimit, atthecostof
ix
x Preface
themorecursorilypresentedtheoreticalbackground.Thebookfrequentlyrefersto
the original, pioneering work that is easier to understand and most often is best
understood today. The intention is to build a bridge to the more recent research
on the same topic where the full range of possibilities of modern instrumentation
and new theory is revealed. I have always tried to follow the four basic rules of
scientific research as postulated by Rene´ Descartes in his famous Discourse on
Method[4]:(1)Donotbelieveanythingthatyoudidnotthinkaboutthoroughlyand
withutmostscrutiny,(2)alwaystrytodecomposecomplexproblemsintosmaller,
lesscomplexparts,(3)afterhavingsolvedthepartialproblems,putthemtogether
again to solve the originaltask, and (4) always be as quantitativeas possible. For
me,rules(1)and(4)seemtobethebottomlineofanyscientificapproach.Therefore
I recommendthatthe readerappliesthese rules, in particularrule (1),to the book
too, and I can only hope that the outcome is not unfavorable for the book. This
mutualproblemwasaddressedalreadybyoneofthefirstGermanphysicists,Georg
Christoph Lichtenberg (1742–1799), when he said: Wenn ein Buch und ein Kopf
zusammenstoßenundesklingthohl,istdasallemalimBuch?,whichmeans:Ifthere
isacollisionofabookandaheadanditsoundshollow,willthissoundalwaysbe
causedbythebook?
Thetenchaptersofthebookarestronglycross-linkedwitheachother.Thereader
isguidedfromthe broader,introductoryissues, suchashistoricalbackgroundand
basicprinciples(Chap.1),tomorespecialtopicslikeinstrumentation(Chap.2)and
qualitativeanalysis(Chap.3),andtothemostessentialtopicssuchasquantitative
analysis (Chap. 4). Extending that issue to optimizing signal intensity (Chap. 5),
whichconsidersangularrelationsandroughnesseffects,thegeneralroleofsignal-
to-noiseratioinoptimizationofcertaintyanddetectionlimitisoutlinedinChap.6.
Beingthefocusofanysurface(andthinfilm)analysis,quantitativecompositional
depthprofiling(destructiveandnon-destructive)ispresentedChap.7.Thefollowing
chapters are of more qualitative character but are nevertheless important for the
analytical strategy. The latter topic is addressed in practical aspects of surface
and interface analysis (Chap. 8), which contains many hints and tips for sample
handling and for solving problems such as charging and beam damage effects.
Some typical examples (Chap. 9) illustrate proper usage of the previous chapters
(Chaps. 3–8). The final chapter, related surface analysis techniques (Chap. 10),
gives an outlook to various methods which often are complementary to AES and
XPS.
Thus,Iliketoencouragethereadertoreadthebookcriticallybutwithopenmind
and optimism. My hopes were already expressed by Friedrich Nietzsche (1844–
1900)inhisbookDiefroehlicheWissenschaft(TheJoyfulScience):
Wagt’smitmeinerKostihrEsser
Morgenschmecktsieeuchschonbesser
Undschonuebermorgengut.
