Ultrafast Investigations of Materials using Angle-Resolved Photoemission Spectroscopy with High ...

189 Pages·2015·11.82 MB·English

Ultrafast Investigations of Materials using Angle-Resolved
Photoemission Spectroscopy with High Harmonic
Generation
by
Adra Victoria Carr
B.S., University of Arizona, 2007
M.S., University of Colorado Boulder, 2011
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
Department of Physics
2015
This thesis entitled:
Ultrafast Investigations of Materials using Angle-Resolved Photoemission Spectroscopy with High
Harmonic Generation
written by Adra Victoria Carr
has been approved for the Department of Physics
Margaret M. Murnane
Prof. Henry C. Kapteyn
Date
The final copy of this thesis has been examined by the signatories, and we find that both the
content and the form meet acceptable presentation standards of scholarly work in the above
mentioned discipline.
iii
Carr, Adra Victoria (Ph.D., Physics)
Ultrafast Investigations of Materials using Angle-Resolved Photoemission Spectroscopy with High
Harmonic Generation
Thesis directed by Prof. Margaret M. Murnane
Knowing the electronic states of materials and how electrons behave in time is essential to
understanding a wide range of physical processes, from surface catalysis and photochemistry to
practical electrical behavior of devices. Combining Angle-Resolved Photoemission Spectroscopy
(ARPES) with short wavelength high-harmonics to drive the photoemission process, allows for the
direct probing of a wide range of electronic states and momenta within a material. Furthermore,
in a pump-probe approach, electron dynamics can be probed by mapping the response of a system
at specific instances after an excitation. I present results from three studies utilizing time-resolved
ARPES, spanning the conventional” approach of mapping electron/hole dynamics of a material
after an excitation - to more exotic experimental schemes that probe fundamental electronic prop-
erties via interferometric attosecond electron spectroscopy and band-bending at semiconductor
interfaces. In addition to providing information on the fundamental behavior of charge carriers and
electronic states in condensed matter, such studies illustrate the versatility of the high harmonic
time-resolved ARPES technique, and demonstrate the potential of this technique to be extended
with new experimental high-resolution and circular-polarization capabilities.
Dedication
For Jing.
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Acknowledgements
This work is the result of the teaching, mentoring, collaboration, patience, and drive of many
great people. I especially thank my advisors, Margaret and Henry, for awarding me incredible
opportunities, academically and professionally, and having unwavering patience in the construction
of a new experiment. I am also grateful to have traveled and collaborated with some of the best
mentors and minds in the surface science community: Martin Aeschlimann (TU Kaiserslautern)
and Michael Bauer (TU Kiel), Dan Dessau (CU Boulder), and Mark Keller (NIST). Thank you
to my mentors at IBM, especially Richard Haight, who has been a pioneer in this field from its
beginning and whose perspectives on science and life have been invaluable.
I have had the pleasure of working with two incredibly talented post-docs during my tenure.
Stefan Mathias, who implemented the initial apparatus that ours currently resembles, has been a
greatpersonalandprofessionalmentor. Thisexperimentwouldnotbepossiblewithouthisexpertise
and courage to tear everything down and start anew. Piotr Matyba has been a great contribution
in offering fresh perspectives and ideas for experiments. He has had tremendous patience and
diligence in seeing the experiment finally produce results and it could not have been done without
him. Thank you to the PES team: Cong Chen and Zhensheng Tao. The experiment is in excellent
hands with their direction and there is assuredly more great science to come.
Jing, this should have been your work. Im sad others wont get to experience late nights in
lab laughing about horrible mistranslations in Chinese. Ethan, Ive been trying to incorporate your
fantasticalviewoftheworldandloveforadventure. Thankyouforgivingmethebestmotivational
speech still ringing in my head: “Go team!” I miss you both tremendously.
vi
I gratefully acknowledge support from the JILA staff, especially the instrument shop staff:
Hans Green, Blaine Horner, Todd Asnicar, Kim Hagen, Tracy Keep, Dave Alchenberger, and Kels
Detra. The realization of the constant redesigns to this experiment would not have been possible
without their fined tuned expertise. To the JILA computing team, especially JR Raith who should
be given a cape for his superhero ability to always have the right replacement part at 8pm or know
exactly which commands to execute when the Windows machines decide to rebel.
To the Kaiserslautern crew: especially Steffen Eich, Sebastian Emmerich, Jurij Urbancic,
Andy Ruffing, and Martin Wiesenmayer. Thank you for making the late night runs way more fun
than they should be and education on all things definitively “German”. Thank you to the past
(esp. Luis Miaja-Avila, Daisy Raymondson, Sterling Backus) and present KM group members.
To Eric, Kevin, Steve, Carrie, Travis, Joe, Jrr, Dan H., Alejandra, Andrew, Dan W., Katie
and Phoenix who are the best support to my sanity. To my roommate here for 6 years, Tara Drake,
who amazingly shares my love of all things ridiculous and is always able to help with late night
existentialcrises. Youarethebestpersontolaughwithaboutsciencenotmakinganysense. Thank
you to Craig Hogle, for much needed dance interludes, coffee breaks, stories, and introduction to
horrible, horrible songs that should not be listened to by anyone.
To my Dad- who taught me that everything is a “project”, nothing is ever a “black box”,
and not to fear taking things apart (while having a few choice swears reserved in case things go
wrong). To my Mom- who instilled curiosity and constant reminders that the world is a really,
really big place to explore. To my big brother, Jake- who is the beautiful dichotomy of being the
constant voice of pragmatism while having airplane/drag racing/boar hunting hobbies that make
me scared just how relative the term “pragmatism” can be. You are a great support and thanks
for reminding me that its ok to have fun occasionally.
Finally, Yance. I 100% would have been unable to do this without you. 9 years and always
willing to talk science, horrible tv shows (even if you spoil the ending to them all), philosophy,
games, and life. After 2 states, 5 houses, innumerable cross country flights, and the inevitable 4
ER visits (Im really sorry Im such a clutz), thank you for being the best copilot on this adventure.
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Contents
Chapter
1 Introduction 1
1.1 Organization of thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 General Theoretical Background 7
2.1 Photoemission Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Angle Resolved Photoemission . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.2 Photoemission: Three step model vs one step model . . . . . . . . . . . . . . 12
2.2 High Harmonic Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1 Semi-Classical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.2 HHG Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.3 Phase Matching in a Capillary Waveguide . . . . . . . . . . . . . . . . . . . . 22
2.3 Advantages of pairing High Harmonics with Photoemission . . . . . . . . . . . . . . 24
2.3.1 Accessible Momentum Range . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.2 Surface Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3.3 Background Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3 Experimental Apparatus and Techniques 29
3.1 Ti:Sapphire Oscillator & Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2 Beamline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2.1 EUV Beamline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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3.2.2 IR Beamline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.2.3 IR Pump Temporal Compression . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 UHV Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3.1 Sample Preparation Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.3.2 Sample Characterization Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.4 ARPES Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.1 Lens System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.2 Hemispherical Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.3 Electron Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.5 Custom Cryogenic Cooling Manipulator and Sample Holder . . . . . . . . . . . . . . 51
3.6 Finding spatial and temporal overlap . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.7 Future Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 Two-Photon Photoelectron Interferometry on Cu(111) 59
4.1 Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.1.1 Single EUV Harmonic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.1.2 Multiple Harmonics- RABITT . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.1.3 Previous Attosecond Studies on Surfaces . . . . . . . . . . . . . . . . . . . . . 69
4.2 RABITT on Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.1 Surface States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.2 Cu(111) Band structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.3 Experimental Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.4 Experimental Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5 Graphene 84
5.1 Theoretical description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
ix
5.2 Graphene on different substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.3 Dynamical Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.4 Chapter Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.5 SiC/ Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.5.1 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5.2 Time resolved Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.6 Ni(111)/Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.6.1 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.6.2 Intercalation of Alkali Atoms . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.6.3 Discussion and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
6 Band bending Studies on InGaAs/high-k/metal Gate Stacks 115
6.1 Technical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.1.1 Band Flattening Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.1.2 C-V/I-V Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
6.2 Experimental Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.3 Surface Cleaning Investigations on InGaAs using Activated Hydrogen . . . . . . . . 125
6.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.4.1 Stack Deposition Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.4.2 Thermal Treatment of stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6.4.3 C-V/ I-V Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
7 Future Outlook and Conclusions 134
7.1 Circular harmonic Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
7.1.1 RABITT studies on Cu(111) . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
7.1.2 Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
7.1.3 Topological Insulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
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7.1.4 Surface-Adsorbate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
7.2 Time-resolved High energy-resolution Studies . . . . . . . . . . . . . . . . . . . . . . 139
7.2.1 Directly resolving interface states in InGaAs . . . . . . . . . . . . . . . . . . 139
7.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Bibliography 141
Appendix
A Supplemental Material 166
A.1 Multilayer Mirror Characterization and Coatings . . . . . . . . . . . . . . . . . . . . 166
A.2 1ω Optical interference unique from RABITT effect . . . . . . . . . . . . . . . . . . 167
A.3 Surface Emission from Cu(111) in RABITT studies . . . . . . . . . . . . . . . . . . . 168
A.4 Fourier Analysis Method- RABITT studies on Cu(111) . . . . . . . . . . . . . . . . . 169
A.5 Details of DFT and Bader Charge Analysis for Na intercalation on Gr/Ni(111) . . . 173