Table Of ContentSpringer Theses
Recognizing Outstanding Ph.D. Research
Jill Guyonnet
Ferroelectric
Domain Walls
Statics, Dynamics, and
Functionalities Revealed
by Atomic Force Microscopy
Springer Theses
Recognizing Outstanding Ph.D. Research
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Jill Guyonnet
Ferroelectric Domain Walls
Statics, Dynamics, and Functionalities
Revealed by Atomic Force Microscopy
Doctoral Thesis accepted by
the University of Geneva, Switzerland
123
Author Supervisor
Dr. JillGuyonnet Prof.Patrycja Paruch
DPMC-MaNEP DPMC-MaNEP
Universityof Geneva Universityof Geneva
Geneva Geneva
Switzerland Switzerland
ISSN 2190-5053 ISSN 2190-5061 (electronic)
ISBN 978-3-319-05749-1 ISBN 978-3-319-05750-7 (eBook)
DOI 10.1007/978-3-319-05750-7
Springer ChamHeidelberg New YorkDordrecht London
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Every wall is a door
—R. W. Emerson
Supervisor’s Foreword
Ferroelectricmaterials,initiallyseenasmerelyacuriosityupontheirdiscoveryin
1920 by Valasek, have become an important feature of the modern technological
landscape. Named in analogy to ferromagnets, although often containing no iron
whatsoever, ferroelectrics are characterised by a non-volatile electric dipole
moment,orpolarisation,whosedirectioncanbeswitchedunderanappliedelectric
field. Like their ferromagnetic counterparts, ferroelectric samples generally com-
prise many regions or domains with different orientation of the polarisation,
separated by interfaces known as domain walls. They also present associated
pyroelectric, piezoelectric and electro-optic properties, allowing their widespread
integration as electromechanical transducers in radar and ultrasound applications,
for second harmonic and sum frequency generation in nonlinear optics, and as
transistor elements in ferroelectric random access memories.
The domain walls, essentially extended topological defects in their parent
ferroelectricphaseinwhichthepolarisationislocallyminimised,werehistorically
perceived as something of a nuisance, contributing to fatigue (a gradual decrease
of the switching response in devices) and, at increasing density in ever-thinner
films, diminishing the total volume of actually ferroelectric material. More
recently,however,itisthedomainwallsthathavebecomeamajorresearchfocus.
Attheseintrinsicallynanoscaleinterfaces,symmetrybreaking,variationsinstrain,
defect segregation, and more complex electronic or structural reconstruction can
lead to radically different physical properties from those presented by the parent
phase.
More generally, the energy cost associated with the formation offerroelectric
domain walls, and their pinning by many different defects inherently present in
thin films, including oxygen vacancies, dislocations, or grain boundaries, allow
them to be described as disordered elastic manifolds. This statistical physics
approach provides a general framework in which the behaviour of systems as
diverse as propagating fractures, wetting lines, burning fronts or surface growth
canbeunderstood.Insuchsystems,thecompetitionbetweenelasticityandpinning
in a fluctuation potential energy landscape gives rise to characteristic roughening
and a complex dynamic response to applied forces. Ferroelectric domain walls
provide ausefulexperimental model system with precise control over the applied
electric field, temperature, and strain, and the ability to influence the type and
vii
viii Supervisor’sForeword
densityofdefectspresentinthesample.Conversely,abetterunderstandingofthis
fundamentalphysicsallowskeyparameterscontrollingdomainswitching,growth,
and stability to be determined, and used to improve the performance of ferro-
electric materials in memory, optics, sensor, and actuator applications.
JillGuyonnet’sthesisexploresboththemorefundamentalaspectsofroughness
scaling offerroelectric domain walls within the disordered elastic system frame-
work, and their localised novel functional behaviour, motivated by potential
nanoelectronic applications, using the relatively simple tetragonal ferroelectric
solid solution of Pb(Zr,Ti)O , widely integrated in modern ferroelectrics tech-
3
nologies, and exploiting the nanoscale resolution of scanned probe microscopy
techniques.
During her doctoral research, Jill identified a novel piezoelectric response at
domain walls, forbidden by symmetry in the parent phase, and which could be
useful in surface acoustic wave transducers based on ferroelectric domain struc-
tures. She also demonstrated domain-wall-specific electrical conduction in this
otherwide insulating material, the first such observation beyond the discovery of
this unexpected phenomenon in the much more complex multiferroic BiFeO ,
3
showing its very general nature. Analysing the roughening of such domain walls
withinafullmultiscalingapproach,Jillalsofoundthatstronglocaldefectsleadto
abreakdownofthesimple,monoaffineroughnessscalingwhichhadbeenassumed
inallpreviousstudiesofthesesystems.Finally,comparingdomainroughnessand
switching dynamics in both ambient conditions and under ultrahigh vacuum, she
was able to elucidate the complex interplay between screening by surface water,
andthepinningbysampledefects,whichtogethercontrolthegrowthrates,aswell
as the final shape and stability of the domains.
The results of this thesis are not only exciting and topical, but should also
appeal to a broad range of interests, from (multi)ferroic studies in condensed
matterphysicstofractureanalysisandsurfacegrowthinstatisticalphysics.Atthe
sametime,thethesisprovidesaclearandeasilyaccessibleintroductiontotherich
and interesting physics offerroelectric domain walls—which we hope you’ll find
as fascinating and as fun as we do.
Geneva, January 2014 Prof. Patrycja Paruch
Acknowledgments
I first wish to express my infinite gratitude to Prof. Patrycja Paruch for accepting
me in her group, back in its early days. Her kindness, availability, keenness, and
supportwereaconstantsourceofmotivation,andIdaresayIamnotexaggerating
when saying I could not have hoped for a more amazing advisor. Thank you,
Patrycja,forenablingmetoworkonsuch excitingresearch topics with such cool
‘‘toys’’, for allowing me to participate to nearly 20 conferences and workshops
during my Ph.D. years, for helping me to considerably hone my communication
skills, but first and foremost for your trust and humanity.
IsincerelythankProf.Jean-MarcTriscone,who mightverywellbethereason
why I have carried on with my studies after my Bachelor degree. When I was a
third year undergrad student, I approached Jean-Marc for information about his
researchforaseminarpresentation.Hisenthusiasmandkindnesslaterledmetoa
summer internship in his group, which in turn led to a Master, and eventually a
Ph.D. thesis under his co-supervision. Thank you, Jean-Marc, for all you
generosity!
Many special thanks to Prof. Thierry Giamarchi, who in addition to being our
theorywellofwisdomhadtoendurealltheexperimentalandtechnicalaspectsof
my thesis. His optimism and insight have been invaluable throughout our efforts
to disentangle some mysteries of disordered elastic systems. Disentangling the
mysteriesbehindhismagicperformances,ontheotherhand,willprobablycontinue
toeludeus.
I warmly thank Prof. Gustau Catalan, not only for accepting to be part of the
jury but also for many fruitful interactions during the course of my thesis and his
general keenness, which I find inspiring.
I am very grateful to Dr. Stéphane Santucci, who was our connection with the
world of fracture physics, thus demonstrating the significant benefits of interdis-
ciplinary exchanges. In this respect, I especially thank him for reading through a
thesis manuscript only partly and loosely related to his area of expertise.
IwishtoaddressveryspecialthankstoElisabethAgoritsas,whoseesinterfaces
everywhere,incoffeestains,inScottishshorelines,inpavementcracks,inclouds,
in bruised apples, and even in domain walls. I have occasionally traded some of
hertimeandwisdomforchocolate,butsheusuallyrefusedtobepaid.Tobeable
to work not only with such an intelligent and patient person but also with one’s
closest friends is a rare gift.
ix
x Acknowledgments
I am extremely grateful to Dr. Sebastián Bustingorry, who gave me my first
contactwithdisorderedelasticsystemswhenIwasstillaMasterstudent,andlater
became one of our key collaborators when we started to incorporate numerical
simulations in our studies. His kindness and impressive enthusiasm have largely
fueled these successful collaborations, and I am truly thankful for everything he
taughtme.IamalsoverygratefulfortheamazingtimespentinBariloche,oneof
my most enriching experiences outside of Geneva. ¡Muchas gracias, Sebastián!
A really big and hearty thank to Iaroslav Gaponenko, for taking some happy
first steps in ophidology with me. Also for the continued taming of our UHV-VT
AFM system, our ‘‘Omicron’’, the machine from heaven with a devilish temper.
And tea. Lots and lots of tea.
Mygratitudeevidentlyextendstoallcurrentandpastmembersofthegroupsof
Patrycja Paruch and Jean-Marc Triscone, nearly all of them having helped me at
some point, and certainly all of them being wonderful people: Benedikt Ziegler,
Yuliya Lisunova, Cédric Blaser, Gijsbert Rispens, Christophe Caillier, Céline
Lichtensteiger, Stefano Gariglio, Pavlo Zubko, Claudia Cancellieri, Alessia
Sambri, Nicolas Reyren, Nicolas Stucki, Andrea Caviglia, Almudena Torres,
Stéphanie Fernandez, Daniela Stornaiuolo, Raoul Scherwitzl, Alexandre Fête,
Denver Li, and Sara Catalano.
My thesis would not be what it is were it not for exceptional technical support
of Sébastien Muller and Marco Lopes, whom I thank most sincerely for their
kindness and help. I also extend my gratitude to Gregory Manfrini, Patrick
Magnin, and Sandro d’Aleo.
I wish to address particular and most sincere thanks to Prof. Michel Decroux,
whom I had the genuine pleasure of assisting in his general physics course for
medical students. That these students have come to enjoy physics and consider it
useful knowledge is a testament to the care he has instilled in his course, which I
find truly inspiring. Michel has also played a significant part in the advancement
forwomenprogram,whichhascertainlyhelpedmotivatemydecisiontoundertake
a Ph.D. thesis. Thank you, Michel, for your extraordinary commitment.
I kindly thank Lidia Favre-Quattropani for her nice support and advices
throughout the years, the good mood in the office, as well as for the nice work I
had the opportunity to do with her on outreach projects.
I wish to express my sincerest gratitude towards our administrative collabora-
tors, Fabienne Hartmeier, Denise Borjon, Esther Schwarz, Nathalie Chaduiron,
and Marianne Gervais, whose help to navigate the treacherous waters of admin-
istration has been essential for survival.
IalsogratefullyacknowledgefinancialsupportfromtheSwissNationalScience
Fundation under MaNEP and Division II, and the financial and academic support
of the University of Geneva.
IthankofcoursealltheGuyonnetclan.GenevièveGuyonnet,whoistheearliest
reasonwhyIcametolovescience.JacquesGuyonnet,whofirsttaughtmetofly,and
has always demonstrated supportand pride during mystudies. Sylvère Guyonnet,
always present and probably wiser than me. Adasol Alsonso-Guyonnet, ¡muchas
