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«By Kannatassen Appavoo Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University in partial fulfillment of the ...»

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HYBRID PHASE-CHANGING NANOSTRUCTURES:

FROM RECONFIGURABLE PLASMONIC DEVICES TO ULTRAFAST DYNAMICS

By

Kannatassen Appavoo

Dissertation

Submitted to the Faculty of the

Graduate School of Vanderbilt University

in partial fulfillment of the requirements

for the degree of

DOCTOR OF PHILOSOPHY

in

Interdisciplinary Materials Science

December, 2012 Nashville, Tennessee

Approved:

Professor Richard F. Haglund Jr.

Professor Sokrates T. Pantelides Professor Sandra J. Rosenthal Professor Jason G. Valentine Professor Sharon M. Weiss Copyright © 2012 by Kannatassen Appavoo All Rights Reserved To mum and dad, For the strength and unquestioning support to let their one and only son be at the antipode of their world to pursue his dreams.

To Professor Haglund, For giving me a shot.

iii

ACKNOWLEDGMENTS

And he who worships them as finite, obtains a finite world, But he worships them as infinite, obtains an infinite world.

~ The Upanishads I still have recollections of being 12 years old and telling friends and family, or whoever would actually listen, that my plan was to move to the United States to pursue my very own geeky American dream: studying science in a high-tech laboratory. To the people and institutions that made this a reality – my parents, Professor Haglund, Khalef, Royal College of Port-Louis, Berea College and Vanderbilt University – thank you.

Above all, my deep sense of gratitude goes to Professor Haglund who is the singular reason for my doctoral work to have seen daylight. I consider myself privileged to have worked with him on a daily basis as his own example of extraordinary hard work is a true inspiration to me and many others. Besides giving me a chance to work in his laboratory, teaching me how to become an independent researcher and showing me the esoteric art of getting a paper published, his trust in me was unparalleled, providing me many a times “carte blanche” on my scientific hunches. To Professor Haglund: I remain indebted to you for the many years or lives to come.

To my committee members – Professors Sokrates T. Pantelides, Sandra J. Rosenthal, Jason G. Valentine and Sharon M. Weiss – I thank you for your time and scientific guidance,

–  –  –

me and encouraging me on a regular basis to collaborate with your respective research groups. I hope that my dissertation truly reflects the extent of my collaboration with each and every one of you. A special “thank you” goes to Professor Valentine for providing me a glimpse of the joys and difficulties in starting a laboratory and for introducing me to metamaterials.

For their support and friendship, I thank the past and present members of the Applied Optical Physics group. I thank Andej Halabica and Ben Lawrie for sharing their love of ultrafast with me and Davon Ferrara and Jed Ziegler for teaching me the art of electronbeam lithography. Without them, many of my projects would not have gotten off the ground. Special thanks go to Joyeeta Nag for her encouraging words and never-ending willingness to collaborate with me, to Dr. Ferrara for providing me with my first scientific obsession: interferometric autocorrelation measurements and Robert Marvel for teaching me that the next generation can be as good, if not better than the previous one. Last but not least, it is said by Isaac Newton that “if I have seen further it is by standing on the shoulders of giants.” Although we have never met, I thank René Lopez for introducing vanadium dioxide to the group, the gift that keeps on giving.

Significant portions of my research were conducted at the Vanderbilt Institute for Nanoscale Science and Engineering facilities and consequently I owe my gratitude to all the VINSE staff. Particularly, I thank Professor Hmelo, Bo Choi, Ben Schmidt and Bob Geil for their extensive training sessions. Their expertise and technical advice proved invaluable throughout my time at Vanderbilt University.

–  –  –

thank Professor Stefan Maier, Dang-Yuan Lei and Yannick Sonnefraud at Imperial College London for their invaluable expertise and advice regarding both single-particle spectroscopy and simulations of complex nanostructures. I thank Ying Xu, Drew Steigerwald, John Kozub and Sergey Avanesyan for help with my first pump-probe experiments at Vanderbilt University. I thank Simon Wall, together with Professor Martin Wolf and Julia Stähler at the Fritz-Haber-Institut der Max-Planck-Gesellschaft for their collaboration and tremendous insights on ultrafast studies of vanadium dioxide. I thank Professor David Hilton and Nathaniel Brady at The University of Alabama at Birmingham and Rohit Pransankumar and Minah Seo at Los Alamos National Laboratory for their direct contribution to the ultrafast studies of hybrid nanomaterial. I thank Professor Philip Willmott and Stephan Pauli of the Synchrotron facility at the Swiss Light Source. I thank the DTRA group members for providing me with a glimpse of a highly complex collaborative research incorporating biology, chemistry and physics. Finally, my heartfelt gratitude goes to Bin Wang, Dang Yuan Lei and Yannick Sonnefraud who have contributed directly in many ways to adding tremendous scientific depth to my doctoral work.





My interest in phase-changing material and pump-probe spectroscopy was spurred by the infectious enthusiasm of the Phase-Change Non-Volatile Memory group at IBM – Almaden Research Division. So, to Delia Milliron, Simone Raoux, Robert Shelby and Bulent Kurdi: thank you as working with you made it clear that experimental physics is what I should be doing.

–  –  –

contributed to shape my views about science: Mr. Thodda, Mr. Chong, Mr. Sungeelee, Prof.

Majumdar, Prof. Powell and Prof Amer. You have not only instilled the love of physics in me but have directly helped get me there. Furthermore, I thank the undergraduates and incoming graduate students who have worked closely with me for their summer research or research rotations: Luke Andrea, Ethan Shapera, Yuanmu Yang and Christina McGahan.

In many ways, my professional development and future career decisions have been influenced by you. On a more personal note, I thank Sarah Satterwhite, Carol Soren, Sandy Childress, René Colehour for getting the not-so-little things done and making my graduate life run as smoothly as it possibly could, till the last minute.

It is amazing to realize the number of people that it takes to get research done, but even more astounding to me is the ability for science to bring people all over the world together. To all the people with whom I have shared a “wall” or an office, thank you for sharing your traditions and beliefs with me. It is remarkable how many countries (USA, India, China, Russia, Nepal, Iran, Venezuela, Spain, England, Slovakia, France and of course Mauritius) can fit in room 6423 of the Stevenson Center… Last but not least, I thank my family back home for their love and support. Few special thanks are also required. To BoJana and Rob, thank you for keeping me sane and healthy on a regular basis, but above all for being my friend through thick and thin; you are the two people that I could not afford to lose during my graduate career. To Bolotbek, Remi, Dikshya, Dhiraj, Rod, Christina, Suraj, Subhav, Praneeta, Alina, Peter, Kenny, Vusal, Yordan, Saylee, Seema, Jordan, Terri, Jack, Tamara, Anurag, Shefali, Joy, Sandy, Steve, Robin, Jim and

–  –  –

on a regular basis, rock climbing and eating momos being the latest ones.

To Shiblee, Enrique, Michaela, Andreea and Pritha., I will not thank you for the lovely distractions from my studies; not even for showing me what living means in its

various ways, shapes and forms outside of the scientific world, but I will thank you for this:

being who you are and staying true to your beliefs, whether or not they made sense to others… Whether one believes there is a God or not who assigns one to a family, I am blessed to have landed into two sets of amazing homes; to Joanne and Pradeep in little town Berea, thank you for providing a home away from home when I needed it the most; to my parents in tiny island Mauritius, thank you for all your support, trust and love. Although these eight years of being away flew by for me, I know it seemed an eternity for you. So to mum and dad, there can only be one thing to say: I love you.

–  –  –

My dissertation is a result of the work funded partly by National Science Foundation (ECEthe Office of Science, US Department of Energy (DE-FG02-01ER45916) and the Defense Threat Reduction Agency (HDTRA1-10-1-0047). Portions of this doctoral work were performed at the Vanderbilt Institute of Nanoscale Science and Engineering, using facilities renovated under NSF ARI-R2 DMR-0963361.

–  –  –

The quest for understanding light-matter phenomena has accompanied the evolution of mankind from almost its origins. As a science, it can be traced as far as the Ancient Greek civilization, when during his studies on visual perception, Aristotle realized the importance of the medium in-between the eye and an object. At the core of our abilities for visual perception is the power of optics which is based on one simple fact – light exhibits the right amount of interaction with matter. Put more scientifically, light quanta lies in the energy range of electronic and vibrational transitions in matter1. For this reason, experiments with light are intuitive and help us to consciously and rationally connect

Abstract

ideas.

Nowadays, the detailed study of light-matter interaction has, as its ultimate goal, the spatial and temporal control of selected modes of electromagnetic radiation to particular material excitations.

Over the last century, the ability to understand complex photon-atom interaction has been greatly challenged. However, thanks to the progress in nanotechnology, scientists are now able to routinely tailor, measure and manipulate the properties of nanostructures at the individual level, thus providing a deeper understanding of the coupling mechanism at play. More importantly, such studies have revealed that as we examine even smallersized structures, new physical effects become prominent, implying their potential prospect

–  –  –

phenomena such as lasing in a single living cell and cloaking, to name a few.

Figure P.1. Potpourri of Tailored Light-Matter Interaction at the Nanoscale. (a) Quenching Brownian motion using plasmonic nanometric optical tweezing;2 (b) Single tailored nanofocus for enhanced gas sensing;3 (c) 3D optical metamaterial for negative refractive index;4 (d) Gold helix for broadband circular polarizer;5 (e) Room-temperature sub-diffraction plasmonic laser;6 (f) Single-cell biological laser;7 (g) Nanoantenna coupled to a quantum dot for directional emission;8 (h) 3D plasmonic rulers to determine distances within chemical or biological species;9 (i) Atomic graphene layer for optical broadband modulation;10 (j) Optical monopole antenna for directing single-molecule emission;11 (k) Carpet cloak made of dielectrics.12 The main motivation of this dissertation is to develop an understanding of reconfigurability in hybrid nanostructures whose optical properties can be uniquely

–  –  –

plasmonics systems – based on quanta of plasmon oscillations derived from coupled electron-photon modes – is achieved by using the kinetics and dynamics of a phasetransforming material. This work demonstrates precisely how functionality hinges on the expertise in tuning the spatial and temporal features of a quantum material vanadium dioxide (VO2). Since these quantum materials offer many “knobs” to control macroscopic phenomena such as high-temperature superconductivity13, colossal magnetoresistance14, multiferroicity15 or metal-insulator transition16, this thesis could potentially be generalized to the study of other classes of hybrid nanomaterials. For example, one of such studies could be the coupling of magnetic responses of split-ring resonator metamaterial17 with manganites to enhance or control magnetic dipole transitions18. We devote this thesis to studying the insulator-to-metal transition in VO2 and its role in optimizing modulation of plasmonic functionality in confined nanoscale volumes and on an ultrafast timescales.

Fundamental intrinsic properties such as electron-electron interaction, electron-phonon coupling and electron-grain-boundary scattering, intimately connected to phenomena such as defect-mediated nucleation, interfacial effects, electron injection or chemical interface damping will be discussed.

Chapter 1 serves as an introduction to both the field of plasmonics and phasechanging vanadium dioxide with a focus on the ultrafast manipulation of such systems.

Since the ultimate goal is device-integration, we introduce in this chapter a novel and reliable deposition method for producing thin films and nanostructures of VO2 using electron-beam evaporation. Combined with the versatile hole-colloidal mask lithography

–  –  –

active substrates could thereafter be implemented in on-chip sensors, catalytic nanodevices or for fundamental ultrafast studies of size-dependent switching in phasechanging material. Since the primary goal of this thesis however is to understand the fundamental properties of such hybrid nanostructures, most structures presented in the subsequent chapters were fabricated by electron-beam lithography for precision.



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