DOCSLIB.ORG

Light Management in Photovoltaics and Photoelectrochemical Cells

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Light Management in Photovoltaics and Photoelectrochemical Cells Light Management in Photovoltaics and Photoelectrochemical Cells using Tapered Micro and Nano Structures Thesis by Sisir Yalamanchili In Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2019 Defended December 5, 2018 © 2018 Sisir Yalamanchili All Rights Reserved i Acknowledgements I would like to begin with thanking Caltech community and the materials science department for the opportunity they provided for me to improve intellectually, professionally, and personally. My last five years at this place has not just made me a better thinker and problem solver, it also gave me the confidence in my abilities and ideas. I am very grateful for my advisers Harry Atwater and Nathan Lewis for giving me the opportunity to be part of their fantastic groups through which I had a chance to find a lot of collaborators for research and some close friends. In these two groups I found a lot like minded individuals who are motivated to find creative solutions for important energy and environment related problems. I want to thank Harry Atwater for constantly encouraging me to go to conferences and network with people, and for being an integral part of the Sunday soccer team. I can only wish to be able to match a twenty something year old in fitness when I am over fifty. I would like to thank Nathan Lewis for giving me all the freedom in the world to figure out my own project, and for dancing and playing games with us after intense scientific discussions during group retreats. Nate’s retreats also gave us, the current members of the group to talk to alumni who are doing wildly different things in their carriers to open our mind to the limitless possibilities. I would like to see this tradition to continue. Being part of two different groups I had access to a lot of facilities without which none of the results that are presented in this thesis would have been possible. I would like to thank both my advisors for making sure I was funded until my last day as a Caltech student. I would like to thank my other thesis committee members, Julia Greer, Bill Johnson, and Bill Goddard, who also served in my candidacy committee for taking time out of their busy schedules and being flexible with my defense date changes. I had the opportunity to take classes that were taught by Julia Greer and Bill Johnson in my first year. As a non-materials science major in a materials science program my learning curve during my first year has been very steep and Julia Greer and Bill Johnson played a major part in it. Most of my time at Caltech has been spent in the Kavli Nanoscience Institute (KNI), without which I wouldn’t have realized any of my devices. I would like to thank all the current and former KNI staff including Guy DeRose, Melissa Melendes, Nils Asplund, Nathan Lee, Bert Mendoza, Steven ii Martinez, Alex Wertheim, and Matthew Hunt for training me on various fabrication equipment and being patient with me while I learnt different techniques. Keeping fabrication equipment always up and running is not an easy task. Therefore, I would like to thank you all the KNI staff for keeping the facility running 24 x 7, 365 days a year. Along with the technical staff there are a lot of non- technical staff without whom no institution can ever run smoothly. Christy Jenstad, Tiffany Kimoto, Jennifer Blankenship, Lyann Lau, Barbara Mirallas, and finally last but not the least Jonathan Gross have been the reason that the two research groups run so smoothly. I would like to say a special thank you to Jonathan who has been a huge help in scheduling my defense talk and making my life easy with conference travel. I want to convey a special thank you for Kimberley Papadontanakis without whom the Lewis group would not function in an organized manner for editing my manuscripts and helping with my next career move. I had a lot of mentors during my time at Caltech without whom my learning would have been much slower. Hal Emmer showed me around in the lab, trained me on many experimental techniques, and has been a mentor in my first couple of years. He let me just walk into his office without notice and disturb him from his work with a lot of questions. Without Hal I would have taken a lot more time to become a productive researcher. Kate Fountaine has continued to be my go-to person whenever I needed some advice and help with optical simulations and writing papers. She has always been enthusiastic to work with me due to our mutual interest in nanowires and nanocones, and without her contributions I would have certainly taken a much longer time to complete my projects. I want to thank Christopher Chen for his help with transmission electron microscopy (TEM) and tolerating me while I fell asleep when he was showing me the TEM sample preparation. I want to thank Shu Hu for asking me to look up alternate ways to make Si microwires. Due to that advice I learnt dry etching techniques which were a main part of me being able to fabricate a lot of interesting structures for my work in this thesis. I want to acknowledge Mita Dasog and Azhar Carim for proving me wrong when I said something in the lines of our project seems to silly and obvious, for their contributions for the paper that is responsible for chapter 4 of this thesis that resulted in a publication in nano letters. Erik Verlage and Sophia Cheng have been an integral part in the TiO2 nanocone project. Looking back at a time when we had no clue about how to fabricate them to ending up realizing a working TiO2 cone device, this project has been a very long journey which, without their important contributions wouldn’t have iii been possible. Sophia has been a very helpful KNI partner who helped me with a lot of electron beam lithography, and her never give up on a hard fabrication project attitude is very infectious. Paul Kempler has been my go-to electrochemistry collaborator, who despite our different working styles made our collaborations fruition into a manuscript. I am looking forward to Paul taking the Si microcones to a new level by realizing future devices using them. During my PhD I have been an integral part of “ETC” team where ETC stands for effectively transparent front contacts. Rebecca Saive has led this project during her time as a post doc in Atwater group. Because of Rebecca reaching out to me for making hard masters I had a chance to be a close witness to an idea starting as a research project and ultimately into a startup led by Thomas Russel, along with multiple publications and patent applications in that process. I am very excited to see how the ETC story unfold in the future. Colton Bukowsky has been an integral part of the ETC team in the earlier years and continued to be a collaborator on SiOX nanocones project which is not included in this thesis. I hope one day he will finish writing that paper :). I want to thank him for letting me play with Napa sometimes. In the past year I had a lot of fun working alongside other ETC team members: Kelly McKenzie, Sophia Coplin, Chris van de stadt, and Michael Kelzenberg. I want to thank Sophia for teaching me the PDMS stamp fabrication secrets. I want to wish Kelly all the best for the ETC project and I hope we will see one new dot on the NREL solar cell efficiency chart in near future; no pressure! I want to thank Chris for gifting me his squash racket which he blamed when he lost a bunch of games to me ;). Before I met Mike Kelzenberg, I only heard stories through Hal, and I am very glad I got a chance to work with him. His unending enthusiasm towards science, his ability to mentor students with a lot of patience, his capacity to handle multiple projects, and his vast knowledge about every random topic are an inspiration. I also thank Mike for organizing many group events which were a lot of fun. Stefan Omelchencko has been my friend and partner in Si / perovskite tandem project that isn’t part of this thesis. We persisted on this project for three years, and finally seeing that fruition into a publication gives me immense satisfaction. Stefan was a constant listener of my rants in the office, and a travel buddy to various conferences and to India. I intentionally skipped detailed acknowledgements to Azhar Carim earlier since I know he is one of the people who will take time to read this :). I want to thank you for introducing me to a lot of places to hangout around Los Angeles, inviting me to “events” at his place, and losing a bet to me over the extent of aerodynamic iv liftoff of a cap when worn while sitting in the back of a convertible car. I am looking forward to the day he defends his thesis. I thank Katie Hamann for being a wonderful office mate and hiking partner to explore hikes around LA over the last couple of years. Madeline Meier is a fellow coffee addict along with Azhar and Katie with whom I got to know almost every coffee place in Pasadena along with a bunch of Asian restaurants. I thank you for joining us in our meat eating expedites despite being a vegetarian with limited options.
Load more

Recommended publications
  • Harry Atwater Is Currently Howard Hughes Professor and Professor of Applied Physics and Materials Science at the California Institute of Technology
    Harry Atwater is currently Howard Hughes Professor and Professor of Applied Physics and Materials Science at the California Institute of Technology. His research interests center around two intertwined research themes photovoltaics and renewable energy and plasmonics and metamaterials. Atwater and his group have been active in photovoltaics research for more than 20 years. Recently they have pioneered new fabrication approaches to III-V semiconductor multijunction cells, and have actively research projects on III-V thin film cells, silicon wire array solar cells, silicon thin film cells and plasmonic light absorber structures. Atwater received his S.B. (1981), S.M. (1983), and Ph.D. (1987) in Electrical Engineering from the Massachusetts Institute of Technology. He currently serves as Director of the Caltech Center for Sustainable Energy Research, and is also Director of the Center for Light-Material Interactions, a DOE Energy Frontier Research Center. Professor Atwater was most recently named as Director of the Resnick Institute. Dr. Atwater has consulted extensively for industry and government, and has actively served the materials community in various capacities, including Material Research Society Meeting Chair (1997), Materials Research Society President (2000), AVS Electronic Materials and Processing Division Chair (1999), and Board of Trustees of the Gordon Research Conferences. He serves on the Director’s Review Committee, Chemistry and Materials Science Division, Lawrence Livermore National Laboratory. He has served on the Department of Energy, Office of Science, Division of Materials Sciences Visiting Committee; Stanford University Department of Materials Science and Engineering Visiting Committee; National Science Foundation Division of Materials Research Visiting Committee. Atwater is founder and chief technical advisor for Alta Device, a solar energy company, and Aonex Corporation, a compound semiconductor materials company.
    [Show full text]
  • Structure, Chemistry, and Energetics of Organic and Inorganic Adsorbates on Ga-Rich Gaas and Gap(001) Surfaces
    Structure, Chemistry, and Energetics of Organic and Inorganic Adsorbates on Ga-Rich GaAs and GaP(001) Surfaces Thesis by Seokmin Jeon In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2014 (Defended September 30, 2013) ii 2014 Seokmin Jeon All Rights Reserved iii “No Pain, No Gain.” iv ACKNOWLEDGEMENTS I remember my wonderful mood when I first visited Caltech as a prospective student. Just before I came to Caltech, I visited the Columbia University, New York for the same purpose. I found everything in Pasadena including weather and people’s attitudes was attractive to me in contrast to what I found in New York. Living and studying in this beautiful place has been my best pleasure. Many individuals have supported, helped, and encouraged me to complete my Ph.D. course at Caltech, so it is my great pleasure to acknowledge them. I would like to thank my advisor, Professor Harry Atwater for his guidance and support. Especially, I appreciate him for providing me a great deal of freedom and independence on my thesis research. He has also shown me the wisdom, leadership, and enthusiasm that a leading scientist owns. My thesis committee, Professors Bill Goddard, Nate Lewis, and Jack Beauchamp are also my role models. It was my pleasure and honor to be advised by such great scientists. Many people in the Atwater group have contributed to the successful completion of my thesis research. Particularly, I would like to thank Jeff Bosco, Victor Brar, Seyoon Kim, Samantha Wilson, Min Jang, Jim Fakonas, Dan Tuner-Evans, Chris Chen, Yulia Tolstova, Hal Emmer, John Lloyd, Carissa Eisler, Siying Peng, Sunita Darbe, Amanda Shing, Imogen Pryce, Michael Kelzenberg, Jonathan Grandidier, Marina Leite, Gerald Miller, Vivian Ferry, Stanley Burgos, Ryan Briggs, Andrew Leenheer, Greg Kimball, Adele Tamboli, Deidre O’Caroll, Domenico Pacifici, Davis Darvish, Morgan Putnam, and Matt Sheldon for sharing their knowledge and skills, having time to discuss about research and science, and being good friends.
    [Show full text]
  • Plasmonics and Metamaterials for Photonics and Solar Energy Conversion
    Plasmonics and Metamaterials for Photonics and Solar Energy Conversion Metamaterials and plasmonic materials have yielded new modes of light localization and dispersion control that are not available in ordinary homogeneous photonic media. These have enabled creation of metallodielectric composites with an enhanced local density of optical states and structures that act as slow light structures, greatly enhancing the degree of optical absorption and spontaneous emission. I will begin by surveying the conditions for plasmonic and artificial magnetic response and the resulting conditions for the optical wavevector, power flow, and phase propagation. Then basic nanophotonic motifs for metamaterial and plasmonic structure design will be introduced. New component materials for metamaterials design will be discussed, including conducting oxides, nitrides and two-dimensional materials such as graphene that give rise to electrical tunability of the complex refractive index, examples of integrated photonic device applications will be given. Further, criteria for plasmonic and metamaterial structures in solar energy conversion will be outlined, including designs to maximize absorption of broadband unpolarized radiation over a wide range of incidence angles, as is needed in solar energy conversion applications. Finally, emerging and future directions for nanophotonics, such as exploiting hot carrier excitation and quantum phenomena will be surveyed. Web Resources: LMI-EFRC: http://lmi.caltech.edu/ Atwater Group: http://daedalus.caltech.edu/ Biography Harry Atwater is the Howard Hughes Professor of Applied Physics and Materials Science at the California Institute of Technology. Professor Atwater received his B. S., M. S. and Ph.D. degrees from the Massachusetts Institute of Technology respectively in 1981, 1983 and 1987, and has been a member of the Caltech faculty since 1988.
    [Show full text]
  • Forty-First DOE Solar Photochemistry P.I. Meeting
    Proceedings of the Forty-First DOE Solar Photochemistry P.I. Meeting Gaithersburg Marriott Washingtonian Center Gaithersburg, Maryland June 3-5, 2019 Chemical Sciences, Geosciences, and Biosciences Division Office of Basic Energy Sciences Office of Science U.S. Department of Energy FOREWORD The 41st Department of Energy Solar Photochemistry Principal Investigators’ Meeting, sponsored by the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences, is being held June 3-5, 2019 at the Washingtonian Marriott in Gaithersburg, Maryland. These proceedings include the meeting agenda, abstracts of the formal presentations and posters, and a list of participants. The Solar Photochemistry Program supports fundamental, molecular-level research on solar energy capture and conversion in the condensed phase and at interfaces. This conference is the annual meeting of the grantees who conduct research with support from this Program. The gathering is intended to facilitate the exchange of ideas and foster collaboration among these researchers. The meeting this year features an invited presentation by Harry Atwater, Director of the Joint Center for Artificial Photosynthesis (JCAP). JCAP is the Department of Energy’s Fuels from Sunlight Energy Innovation Hub, a multi-investigator research and development center that was established in 2010 and renewed in 2015. Its mission is currently focused on creating a scientific foundation for the solar-driven conversion of carbon dioxide into renewable transportation fuels. Prof. Atwater will tell us about recent JCAP discoveries and research accomplishments. I would like to express my thanks to Justin Johnson who continues to spend part of his time as a detailee for the Solar Photochemistry Program, assisting with numerous critical behind-the- scenes tasks.
    [Show full text]
  • PDF (One-Sided Printing Format)
    Hybrid Silicon Nanophotonic Devices: Enhancing Light Emission, Modulation, and Confinement Thesis by Ryan Morrow Briggs In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2011 (Defended May 13, 2011) c 2011 Ryan Morrow Briggs All Rights Reserved ii To Hannah. iii Acknowledgements With immense gratitude, I first acknowledge my advisor, Professor Harry Atwater, for his support, encouragement, and enthusiasm. Harry is the source of an incredible number of great ideas and visionary scientific contributions, but he also allows his students to own their thesis work in a way that fosters personal and professional growth. Looking back on the past five years, I realize that I would not have had my graduate school experience be any other way. To this day, Harry amazes me with his ability to deeply understand ideas and immediately expand on them with his pithy insights, but he also amazes me with his genuine regard and concern for other people, particularly the members of his group at Caltech. I am eager to see how Harry, his research group, and his entrepreneurial ventures will continue to impact the world in the years to come. I am also extremely grateful to Professors Oskar Painter, Julia Greer, Amnon Yariv, and Bill Goddard for serving on my candidacy and thesis committees. It is an honor, but also a humbling experience, to prepare a thesis knowing that it will be examined by individuals who are eminent experts in their fields, and I thank them for their time and input. Within the Atwater group, I must first thank Ken Diest for teaching me how to survive in the lab, figuratively and perhaps literally.
    [Show full text]
  • Harry Atwater Is the Howard Hughes Professor of Applied Physics and Materials Science at the California Institute of Technology
    Harry Atwater is the Howard Hughes Professor of Applied Physics and Materials Science at the California Institute of Technology. Professor Atwater currently serves as Director of the DOE Joint Center for Artificial Photosynthesis. Atwater’s scientific interests have two themes: photovoltaics and solar energy as well as plasmonics and optical metamaterials. His group has created new high efficiency solar cell designs, and have developed principles for light management in solar cells. Atwater is an early pioneer in nanophotonics and plasmonics; he gave the name to the field of plasmonics in 2001. He has authored or co- authored more than 400 publications cited in aggregate > 33,000 times and his group’s advances in the solar energy and plasmonics field have been reported in Scientific American, Science, Nature Materials, Nature Photonics and Advanced Materials. He is co-founder and chief technical advisor for Alta Devices, a venture-backed company in Santa Clara, CA, that holds the current world record for 1 Sun single junction solar cell efficiency and that is currently transitioning high efficiency/low cost GaAs photovoltaics technology to manufacturing and large-scale production. He serves as Editor in Chief for the journal ACS Photonics, and is Associate Editor for the IEEE Journal of Photovoltaics, and in 2006 he founded the Gordon Research Conference on Plasmonics, which he served as chair in 2008. Harry Atwater is a Fellow of the Materials Research Society, and Member of US National Academy of Engineering. Atwater has been honored by awards, including: (2014) Julius Springer Prize in Applied Physics, (2014) ISI Highly Cited Researcher, (2013) Fellowship from the Royal Netherlands Academy of Arts and Sciences, (2012) ENI Prize for Renewable and Non-conventional Energy, SPIE Green Photonics Award (2012), MRS Kavli Lecturer in Nanoscience (2010), the Popular Mechanics Breakthrough Award (2010).
    [Show full text]
  • Program Agenda 4
    Fitzpatrick Institute for Photonics Ç Seventh Annual Meeting Symposium on Photonics in the Translational Era: Science and Technology for a Purpose Ç Table of Contents Page Number Program Agenda 4 Speaker Abstracts & Biographical Sketches 7 Poster Session 39 Themed Lab Tours 72 Industry Booths – Corporate Partners of FIP 74 The Fitzpatricks 76 Faculty at FIP 77 (including departments, institutions and research programs) www.fitzpatrick.duke.edu - 3 - Fitzpatrick Institute for Photonics Ç Seventh Annual Meeting Photonics in the Translational Era: Science and Technology for a Purpose Ç Program Agenda ~ Thursday, October 11, 2007 ~ Duke University, FCIEMAS, Fitzpatrick Building, Schiciano Auditorium 8:00 – 9:00am Registration and Continental Breakfast 9:00 – 9:10am Opening Address Peter Lange, Provost, Duke University 9:10 – 9:30am Introductory Remarks Rob Clark, Dean, Pratt School of Engineering, Duke University Tuan Vo-Dinh, Director, Fitzpatrick Institute for Photonics (FIP), Duke University 9:30 – 10:00am Symposium Keynote Lecture John H. Marburger, III, Science Advisor to the President, Director, Office of Science and Technology Policy Executive Office of the President of The United States of America 10:00 – 10:30am Plenary Lecture Sir John B. Pendry, Chair, Theoretical Solid State Physics Imperial College, London, United Kingdom ”Transformation Optics: Designing Optics on the Nanoscale” 10:30 – 11:00am Coffee Break/ Industry & Poster Sessions 11:00 – 12:10pm Session 1 Advanced Photonics Chair, Adam Wax, Duke University David Smith,
    [Show full text]
  • Lawrence Berkeley National Laboratory Recent Work
    Lawrence Berkeley National Laboratory Recent Work Title Spatiotemporal Imaging of Thickness-Induced Band-Bending Junctions. Permalink https://escholarship.org/uc/item/5pn61484 Journal Nano letters, 21(13) ISSN 1530-6984 Authors Wong, Joeson Davoyan, Artur Liao, Bolin et al. Publication Date 2021-07-01 DOI 10.1021/acs.nanolett.1c01481 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Spatiotemporal Imaging of Thickness-Induced Band Bending Junctions 1 1,2 3,4 5 6 7 Joeson Wong , Artur R. Davoyan , Bolin Liao , Andrey Krayev , Kiyoung Jo , Eli Rotenberg , Aaron Bostwick7, Chris Jozwiak7, Deep Jariwala1,6, Ahmed Zewail3, ǂ, Harry A. Atwater1, * 1. Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, CA, USA 2. Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA, USA 3. Department of Chemistry, California Institute of Technology, Pasadena, CA, USA 4. Department of Mechanical Engineering, University of California, Santa Barbara, CA, USA 5. Horiba Scientific, Novato, CA, USA 6. Department of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA 7. Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA, USA ǂ Deceased *Corresponding Author: Harry A Atwater ([email protected]) ABSTRACT: Van der Waals materials exhibit naturally passivated surfaces and can form versatile heterostructures, enabling observation of carrier transport mechanisms not seen in three- dimensional materials. Here we report observation of a “band bending junction”, a new type of semiconductor homojunction whose surface potential landscape depends solely on a difference in thickness between the two semiconductor regions atop a buried heterojunction interface. Using MoS2 on Au to form a buried heterojunction interface, we find that lateral surface potential differences can arise in MoS2 from the local extent of vertical band bending in thin and thick MoS2 regions.
    [Show full text]
  • Spatiotemporal Imaging of Thickness-Induced Band Bending Junctions
    Spatiotemporal Imaging of Thickness-Induced Band Bending Junctions 1 1,2 3,4 5 6 7 Joeson Wong , Artur R. Davoyan , Bolin Liao , Andrey Krayev , Kiyoung Jo , Eli Rotenberg , Aaron Bostwick7, Chris Jozwiak7, Deep Jariwala1,6, Ahmed Zewail3, ǂ, Harry A. Atwater1, * 1. Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, CA, USA 2. Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, CA, USA 3. Department of Chemistry, California Institute of Technology, Pasadena, CA, USA 4. Department of Mechanical Engineering, University of California, Santa Barbara, CA, USA 5. Horiba Scientific, Novato, CA, USA 6. Department of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA 7. Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA, USA ǂ Deceased *Corresponding Author: Harry A Atwater ([email protected]) ABSTRACT: Van der Waals materials exhibit naturally passivated surfaces and can form versatile heterostructures, enabling observation of carrier transport mechanisms not seen in three- dimensional materials. Here we report observation of a “band bending junction”, a new type of semiconductor homojunction whose surface potential landscape depends solely on a difference in thickness between the two semiconductor regions atop a buried heterojunction interface. Using MoS2 on Au to form a buried heterojunction interface, we find that lateral surface potential differences can arise in MoS2 from the local extent of vertical band bending in thin and thick MoS2 regions. Using scanning ultrafast electron microscopy, we examine the spatiotemporal dynamics of photogenerated charge carriers and find that lateral carrier separation is enabled by a band bending junction, which is confirmed with semiconductor transport simulations.
    [Show full text]
  • How to Drive Light Round the Wrong Bend
    NEWS NATURE|Vol 445|25 January 2007 How to drive light round the wrong bend Can visible light ever be manipulated so that it bends the wrong way? If it could, a range of futuristic devices would be tantalizingly close NEGATIVE RESULT to reality, such as a lens for imaging features Researchers used surface plasmons to carry View from above light across a gold prism — achieving the first Negatively smaller than the wavelength of light, or a shield refracted negative refraction of visible light. wave to render objects invisible. Surface Several scientists have written off such ‘nega- Slit plasmon Normal wave tive refraction’ in the visible range as practically Visible light impossible but a group is now claiming to have enters through slit Positively achieved it, spurring a debate about what con- refracted stitutes true refraction. wave Light bends in a specific way when it passes Silver Silver from one medium to another — an effect called refraction. Negative refraction describes a situ- Surface plasmons 50 nm When surface plasmons ation in which light bends the opposite way. created which emerge from the prism, It happens only if the direction in which the carry the light they are negatively refracted (see inset) peaks and troughs travel along a light wave can 500 nm Gold be reversed relative to the direction in which Silicon nitride the wave itself is travelling. A material with a negative refractive index Silver would focus light perfectly instead of dispers- ing it. This led John Pendry of Imperial Col- lege London to predict that a ‘perfect’ lens could be made, which would image features smaller But achieving similar effects for visible light unveiled a material that they say has a negative than the wavelength of light.
    [Show full text]
  • The Next Wave | Vol
    Vol. 20 | No. 3 | 2014 Forecasting faster, more powerful, and more secure technology At a Glance | Pointers | Spinouts This Z antenna tested at the National Institute of Standards and Technology is smaller than a standard antenna with comparable properties. Its high eciency is derived from the “Z element” inside the square that acts as a metamaterial, greatly boosting the signal sent over the air. The square is 30 millimeters on a side. Innovation in materials science: Electromagnetic metamaterials Jane E. Heyes | Nathaniel K. Grady | Diego A. R. Dalvit | Antoinette J. Taylor aterial properties aect the propagation found in nature, metamaterials have the potential of electromagnetic (EM) waves in to aid in the creation of ultrathin planar lenses, Mprofound ways, which has allowed for superresolution microscopes, compact antennas, devices ranging from eyeglasses to radar to ber- faster computer chips, and surfaces that radically optic cables. However, there are a limited number alter or cloak the EM signature of an object (e.g., an of responses found in natural materials. How can invisibility cloak). the range of possibilities be expanded? Enter EM e limitations of natural materials are a major metamaterials. obstacle that must be overcome to meet the ever- EM metamaterials are composites built increasing demand for faster, lighter, cheaper, and from a structured combination of conductors, more compact devices, making metamaterials semiconductors, and insulators. e individual an important and timely tool for meeting future features make up an ordered array smaller than technology needs. the wavelengths of radiation they are designed to aect, so the EM wave responds to the overall Background combination of these individual structures as if it were an eectively homogeneous material.
    [Show full text]
  • Tunable and Quantum Plasmonic Materials
    McCormick Northwestern Engineering Materials Science and Engineering 2014 DORN MEMORIAL LECTURE Harry A. Atwater Professor of Applied Physics and Materials Science California Institute of Technology Tuesday, January 21, 2014 Tech L211, 4:00pm Reception to follow Cook Hall - Atrium, 5:15pm “Tunable and Quantum Plasmonic Materials” Understanding the fundamental properties of plasmonic and dielectric materials in resonant subwavelength structures has fueled an explosion of interest in metamaterials and nanophotonic devices. In this seminar, we explore new directions for plasmonics by examining the relationship between plasmons and the electrochemical potential of the electron gas, and we discuss opportunities to observe quantum coherent states in plasmonic structures. Usually plasmons are described in a classical electromagnetic theory context, yet plasmons are fundamentally quantum excitations. Moreover, the carrier density and optical properties of plasmonic materials are typically fixed at the time of fabrication. Field effect tuning of the electrochemical potential in graphene nanoresonators enables the plasmon and phonon dispersion to be measured. Electrochemical and carrier density modulation in metals yields tunable resonances in metal nanostructures and reveals the plasmoelectric effect, a newly-discovered photoelectrochemical potential. By tuning the permittivity and index to near-zero values, expands the length scale over which coherent quantum emitter phenomena (e.g., concurrence, superradiance) can be observed in epsilon-near-zero
    [Show full text]