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Ultrafast Investigations of Materials Using Angle-Resolved Photoemission Spectroscopy with High Harmonic Generation

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Ultrafast Investigations of Materials Using Angle-Resolved Photoemission Spectroscopy with High Harmonic Generation 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. v 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 great personal and professional mentor. This experiment would not be possible without his expertise 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 fantastical view of the world and love for adventure. Thank you for giving me the best motivational 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 existential crises. You are the best person to laugh with about science not making any sense. 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. vii 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 viii 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 x 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 1! 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) .
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