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Articles 1 - 30 of 38

Full-Text Articles in Nanoscience and Nanotechnology

On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis Jan 2019

On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The design of metamaterials, which are artificial materials that can offer unique electromagnetic properties, is based on the excitation of strong resonant modes. Unfortunately, material absorption—mainly due to their metallic parts—can damp their resonances and hinder their operation. Incorporating a gain material can balance these losses, but this must be performed properly, as a reduced or even eliminated absorption does not guarantee loss compensation. Here we examine the possible regimes of interaction of a gain material with a passive metamaterial and show that background amplification and loss compensation are two extreme opposites, both of which can lead to ...


Probing Magnetism In 2d Van Der Waals Crystalline Insulators Via Electron Tunneling, D. R. Klein, D. Macneill, J. L. Lado, D. Soriano, E. Navarro-Moratalla, K. Watanabe, T. Taniguchi, S. Manni, Paul C. Canfield, J. Fernández-Rossier, P. Jarillo-Herrero Jun 2018

Probing Magnetism In 2d Van Der Waals Crystalline Insulators Via Electron Tunneling, D. R. Klein, D. Macneill, J. L. Lado, D. Soriano, E. Navarro-Moratalla, K. Watanabe, T. Taniguchi, S. Manni, Paul C. Canfield, J. Fernández-Rossier, P. Jarillo-Herrero

Ames Laboratory Accepted Manuscripts

Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and interlayer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra ...


Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou Mar 2018

Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou

Xiaoshan Xu Papers

Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo ...


Parallel Algorithms For Time Dependent Density Functional Theory In Real-Space And Real-Time, James Kestyn Jan 2018

Parallel Algorithms For Time Dependent Density Functional Theory In Real-Space And Real-Time, James Kestyn

Doctoral Dissertations

Density functional theory (DFT) and time dependent density functional theory (TDDFT) have had great success solving for ground state and excited states properties of molecules, solids and nanostructures. However, these problems are particularly hard to scale. Both the size of the discrete system and the number of needed eigenstates increase with the number of electrons. A complete parallel framework for DFT and TDDFT calculations applied to molecules and nanostructures is presented in this dissertation. This includes the development of custom numerical algorithms for eigenvalue problems and linear systems. New functionality in the FEAST eigenvalue solver presents an additional level of ...


Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin Dec 2017

Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin

Theses and Dissertations

Chalcogen-based layered superconductors with a litharge structure such as FeS and FeSe mono-layers undergo structural and superconducting phase transitions that are tunable by doping. Representing another material platform with a litharge structure but without valence d-electrons, SnO monolayers also display a structural ground state with a degenerate rectangular unit cell at zero temperature and a charge-tunable energy barrier that leads to a thermally-controllable structural phase change. Doped SnO monolayers with rectangular degenerate unit cells give rise to two-dimensional multiferroicity. Their two-dimensional elastic energy landscape adopts a basic analytic expression that is employed to discuss this structural transition. The results contained ...


Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha Dec 2017

Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha

Doctoral Dissertations

The narrow hydrophobic interior of a carbon nanotube (CNT) poses a barrier to the transport of water and ions, and yet, unexpectedly, numerous experimental and simulation studies have confirmed fast water transport rates comparable to those seen in biological aquaporin channels. These outstanding features of high water permeability and high solute rejection of even dissolved ions that would typically require a lot of energy for separation in commercial processes makes carbon nanotubes an exciting candidate for desalination membranes. Extending ion exclusion beyond simple mechanical sieving by the inclusion of electrostatics via added functionality to the nanotube bears promise to not ...


Elastic Properties Of Superconductors And Materials With Weakly Correlated Spins, Christian Binek Jul 2017

Elastic Properties Of Superconductors And Materials With Weakly Correlated Spins, Christian Binek

Christian Binek Publications

It is shown that in the ergodic regime, the temperature dependence of Young’s modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young’s modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Constant diamagnetic susceptibility gives rise to a temperature independent elastic modulus for ceramic and single crystalline superconductors alike. The thermodynamic approach established in this report, paves the ...


Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson Mar 2017

Progress Towards Terahertz Acoustic Phonon Generation In Doping Superlattices, Thomas E. Wilson

Thomas E. Wilson

Progress is described in experiments to generate coherent terahertz acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation. Future experiments are proposed that would use the superlattice as a transducer in a terahertz cryogenic acoustic reflection microscope with sub-nanometer resolution.


Tunable Controlled Release Of Molecular Species From Halloysite Nanotubes, Divya Narayan Elumalai Apr 2016

Tunable Controlled Release Of Molecular Species From Halloysite Nanotubes, Divya Narayan Elumalai

Doctoral Dissertations

Encouraged by potential applications in rust coatings, self-healing composites, selective delivery of drugs, and catalysis, the transport of molecular species through Halloysite nanotubes (HNTs), specifically the storage and controlled release of these molecules, has attracted strong interest in recent years. HNTs are a naturally occurring biocompatible nanomaterial that are abundantly and readily available. They are alumosilicate based tubular clay nanotubes with an inner lumen of 15 nm and a length of 600-900 nm. The size of the inner lumen of HNTs may be adjusted by etching. The lumen can be loaded with functional agents like antioxidants, anticorrosion agents, flame-retardant agents ...


An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur Jan 2016

An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur

Dissertations, Master's Theses and Master's Reports

Evaporation is ubiquitous in nature and occurs even in a microgravity space envi- ronment. Long term space missions require storage of cryogenic propellents and an accurate prediction of phase change rates. Kinetic theory has been used to model and predict evaporation rates for over a century but the reported values of accommodation coefficients are highly inconsistent and no accurate data is available for cryogens. The proposed study involves a combined experimental and computational approach to ex- tract the accommodation coefficients. Neutron imaging is used as the visualization technique due to the difference in attenuation between the cryogen and the metallic ...


Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins Jan 2016

Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins

Doctoral Dissertations

Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions.

In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these ...


Uv Light-Induced Aggregation Of Titania Submicron Particles, Can Zhou, Yashar Bashirzadeh, Timothy A. Bernadowsky Jr., Xiaoyu Zhang Jan 2016

Uv Light-Induced Aggregation Of Titania Submicron Particles, Can Zhou, Yashar Bashirzadeh, Timothy A. Bernadowsky Jr., Xiaoyu Zhang

Mechanical & Aerospace Engineering Faculty Publications

In this study, aggregation of TiO2 (rutile and anatase) submicron particles in deionized (DI) water under ultra-violet (UV) light irradiation was investigated. While no aggregation was observed in the dark, rutile and anatase submicron particles started aggregating upon application of UV light and ceased aggregation in about 2 and 8.4 h, respectively. It has been demonstrated that UV light directly mitigated the particle mobility of TiO2, resulting in a neutralization effect of the Zeta potential. It was also observed that rutile particles aggregated much faster than anatase particles under UV radiation, indicating that the Zeta potential of ...


Local Heating With Lithographically Fabricated Plasmonic Titanium Nitride Nanoparticles, Urcan Guler, Justus Ndukaife, Gururaj Naik, Agbai Nnanna, Alexander Kildishev, V. Shalaev, Alexandra Boltasseva Jul 2015

Local Heating With Lithographically Fabricated Plasmonic Titanium Nitride Nanoparticles, Urcan Guler, Justus Ndukaife, Gururaj Naik, Agbai Nnanna, Alexander Kildishev, V. Shalaev, Alexandra Boltasseva

U. Guler

Titanium nitride is considered a promising alternative plasmonic material and is known to exhibit localized surface plasmon resonances within the near-infrared biological transparency window. Here, local heating efficiencies of disk-shaped nanoparticles made of titanium nitride and gold are compared in the visible and near-infrared regions numerically and experimentally with samples fabricated using e-beam lithography. Results show that plasmonic titanium nitride nanodisks are efficient local heat sources and outperform gold nanodisks in the biological transparency window, dispensing the need for complex particle geometries.


Nanoparticle Plasmonics: Going Practical With Transition Metal Nitrides, U. Guler, V. M. Shalaev, A. Boltasseva Apr 2015

Nanoparticle Plasmonics: Going Practical With Transition Metal Nitrides, U. Guler, V. M. Shalaev, A. Boltasseva

U. Guler

Promising designs and experimental realizations of devices with unusual properties in the field of plasmonics have attracted a great deal of attention over the past few decades. However, the high expectations for realized technology products have not been met so far. The main complication is the absence of robust, high performance, low cost plasmonic materials that can be easily integrated into already established technologies such as microelectronics. This review provides a brief discussion on alternative plasmonic materials for localized surface plasmon applications and focuses on transition metal nitrides, in particular, titanium nitride, which has recently been shown to be a ...


Plasmonics On The Slope Of Enlightenment: The Role Of Transition Metal Nitrides, U. Guler, A. Kildishev, A. Boltasseva, V. Shalaev Jan 2015

Plasmonics On The Slope Of Enlightenment: The Role Of Transition Metal Nitrides, U. Guler, A. Kildishev, A. Boltasseva, V. Shalaev

U. Guler

The key problem currently faced by plasmonics is related to material limitations. After almost two decades of extreme excitement and research largely based on the use of noble metals, scientists have come to a consensus on the importance of exploring alternative plasmonic materials to address application-specific challenges to enable the development of new functional devices. Such a change in motivation will undoubtedly lead to significant advancements in plasmonics technology transfer and could have a revolutionary impact on nanophotonic technologies in general. Here, we report on one of the approaches that, together with other new material platforms, mark an insightful technology-driven ...


Uncovering New Thermal And Mechanical Behavior At The Nanoscale Using Coherent Extreme Ultraviolet Light, Kathleen Marie Hoogeboom-Pot Jan 2015

Uncovering New Thermal And Mechanical Behavior At The Nanoscale Using Coherent Extreme Ultraviolet Light, Kathleen Marie Hoogeboom-Pot

Physics Graduate Theses & Dissertations

Tremendous recent progress in nanofabrication capabilities has made high-quality single-atomic layers and nanostructures with dimensions well below 50 nm commonplace, enabling unprecedented access to materials at the nanoscale. However, tools and techniques capable of characterizing the properties and function of nanosystems are still quite limited, leaving much of the fundamental physics that dominates material behavior in the deep nano-regime still unknown. Further understanding gained by studying nanoscale materials is critical both to fundamental science and to continued technological development. This thesis applies coherent extreme ultraviolet (EUV) light from tabletop high harmonic generation to study nanoscale systems on their intrinsic length ...


Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez Jan 2015

Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez

Open Access Theses & Dissertations

Cadmium Telluride is a material widely used in terrestrial thin film photovoltaic applications due to its nearly ideal band gap (~1.5 eV) and high absorption coefficient. Due to its low manufacturing cost, this technology has the potential to become a significant energy resource if higher energy conversion efficiencies are achieved. However, the module efficiencies (~14%) are still far from the theoretical maximum (~30%) for this material in a single junction configuration. The reason behind this low performance is attributed to the high number of defects that are present within the device materials. The physics behind the formation mechanisms of ...


Photoelectric Characterization Of Bacteriorhodopsin Reconstituted In Lipid Bilayer Membrane, Joel Kamwa Dec 2014

Photoelectric Characterization Of Bacteriorhodopsin Reconstituted In Lipid Bilayer Membrane, Joel Kamwa

Theses and Dissertations

The objective of this work was to conduct basic research in biologically inspired energy conversion solutions. A photosynthetic protein (Bacteriorhodopsin) was reconstituted in a bi-layer membrane. Then, when a laser beam was shined on the membrane, the photon energy was used by the protein to pump protons across the membrane. The translocation of protons across the membrane was measured as photocurrent. For this purpose, a system was built to characterize the lipid bilayer membranes and to measure the photocurrent. The lipid bilayer membrane was characterized by its capacitance and resistance. A picoampere photocurrent was observed when Bacteriorhodopsin protein was present ...


Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta Oct 2014

Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta

Open Access Dissertations

Along with the revolutionary discovery and development of carbon nanostructures, such as carbon nanotubes and graphitic sheets, has arrived the potential for their application in the fields of medicine, bioscience and engineering due to their exceptional structural, thermal and electrical properties. As roll-to-roll plasma deposition systems begin to provide means for large scale production of these nanodevices, a detailed understanding of the environment responsible for their synthesis is imperative in order to more accurately design and control the growth of carbon nanodevices. To date, the understanding of the chemistry and kinetics that govern the synthesis of carbon nanodevices is only ...


Nickel Aluminum Shape Memory Alloys Via Molecular Dynamics, Keith Ryan Morrison Jul 2014

Nickel Aluminum Shape Memory Alloys Via Molecular Dynamics, Keith Ryan Morrison

Open Access Theses

Shape memory materials are an important class of active materials with a wide range of applications in the aerospace, biomedical, and automobile industries. These materials exhibit the two unique properties of shape memory and superelasticity. Shape memory is the ability to recover its original shape by applying heat after undergoing large deformations. Superelasticity is the ability to undergo large, reversible deformations (up to 10%) that revert back when the load is removed. These special properties originate from a reversible, diffusionless solid-solid phase transformation that occurs between a high temperature austenite phase and a low temperature martensite phase. The development of ...


Modeling The High-Speed Switching Of Far-Infrared Radiation By Photoionization In A Semiconductor, Thomas E. Wilson Feb 2014

Modeling The High-Speed Switching Of Far-Infrared Radiation By Photoionization In A Semiconductor, Thomas E. Wilson

Thomas E. Wilson

Data from an earlier study [T. Vogel et al., Appl. Opt. 31, 329 (1992)] on the subnanosecond switching of 119-μm radiation in high-resistivity silicon by pulsed UV laser radiation, is compared with a refined one-dimensional numerical multilayer model accounting for the generation, recombination, and diffusion of the free carriers on the resulting far-infrared optical properties of the silicon. The inclusion of recent measurements for carrier-density and temperature-dependent transport parameters leads to improved agreement between experiment and theory.


Superlattice Ultrasonic Generation, Thomas E. Wilson, M. Oehme, E. Kasper, H-J. L. Gossmann Feb 2014

Superlattice Ultrasonic Generation, Thomas E. Wilson, M. Oehme, E. Kasper, H-J. L. Gossmann

Thomas E. Wilson

We report the first experimental evidence for the resonant excitation of coherent high-frequency acoustic phonons in semiconducting doping superstructures by far-infrared laser radiation. After a grating-coupled delta-doped silicon doping superlattice is illuminated with ~1 kW/mm2 nanosecond-pulsed 246 GHz laser radiation, a delayed nanosecond pulse is detected by a superconducting bolometer at a time corresponding to the appropriate time-of-flight for ballistic longitudinal acoustic phonons across the (100) silicon substrate. The absorbed phonon power density in the microbolometer is observed to be ~10 μW/mm2, in agreement with theory. The phonon pulse duration also matches the laser pulse duration. The absence ...


Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd Feb 2014

Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd

Thomas E. Wilson

The study is based on the success in obtaining the first experimental evidence for the direct excitation of coherent nanosecond-pulsed high-frequency acoustic phonons in semiconducting doping superstructures by electromagnetic fields of the same frequency. Acoustic phonons are detected by a superconducting bolometer, with nanosecond resolution, at the appropriate time-of-flight across a (100) silicon substrate for ballistic longitudinal phonons when a silicon delta-doped doping superlattice is illuminated with grating-coupled nanosecond-pulsed 246-GHz laser radiation with an approximate power density of 1 kW/mm2. The absorbed phonon power density in the bolometer detector is estimated to be 10 μW/mm2, in agreement with ...


Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson Feb 2014

Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson

Thomas E. Wilson

We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using imagereversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. [1], and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of ...


Local Optoelectronic Properties Of Zinc-Porphyrin/Gold Molecular Interfaces, Xi Chen Jan 2014

Local Optoelectronic Properties Of Zinc-Porphyrin/Gold Molecular Interfaces, Xi Chen

Publicly Accessible Penn Dissertations

This research consists in designing a series of experiments to determine the molecular orbital energy levels of zinc-porphyrin molecule when vertically attached to Au(111) substrate. To study the zinc-porphyrine molecular orbitals we use visible light of different wavelengths. Thiolated zinc-porphyrin oligomer molecules link to Au(111) surface, embedded within an 1-octanethiol self-assembled monolayer. Current-Voltage characterization technique allow us to determine the electronic orbital structures of different zinc-porphyrin oligomer single molecules via scanning tunneling microscope. Coupling lasers of different wavelengths and the tunneling junction, illumination effect on the molecular orbital energy levels of zinc-porphyrin molecules is investigated. The results indicate ...


Near-Infrared Surface-Enhanced Fluorescence Using Silver Nanoparticles In Solution, Michael D. Furtaw Dec 2013

Near-Infrared Surface-Enhanced Fluorescence Using Silver Nanoparticles In Solution, Michael D. Furtaw

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Fluorescence spectroscopy is a widely used detection technology in many research and clinical assays. Further improvement to assay sensitivity may enable earlier diagnosis of disease, novel biomarker discovery, and ultimately, improved outcomes of clinical care along with reduction in costs. Near-infrared, surface-enhanced fluorescence (NIR-SEF) is a promising approach to improve assay sensitivity via simultaneous increase in signal with a reduction in background. This dissertation describes research conducted with the overall goal to determine the extent to which fluorescence in solution may be enhanced by altering specific variables involved in the formation of plasmonactive nanostructures of dye-labeled protein and silver nanoparticles ...


Transparent Actuator Made With Few Layer Graphene Electrode And Dielectric Elastomer, For Variable Focus Lens, Taeseon Hwang, Hyeok-Yong Kwon, Joon-Suk Oh, Jung-Pyo Hong, Seung-Chul Hong, Youngkwan Lee, Hyouk Ryeo Choi, Kwang J. Kim, Mainul Hossain Bhuiya, Jae Do Nam Jan 2013

Transparent Actuator Made With Few Layer Graphene Electrode And Dielectric Elastomer, For Variable Focus Lens, Taeseon Hwang, Hyeok-Yong Kwon, Joon-Suk Oh, Jung-Pyo Hong, Seung-Chul Hong, Youngkwan Lee, Hyouk Ryeo Choi, Kwang J. Kim, Mainul Hossain Bhuiya, Jae Do Nam

Mechanical Engineering Faculty Publications

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed inN-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes.The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study ...


Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd Sep 2012

Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd

Physics Faculty Research

The study is based on the success in obtaining the first experimental evidence for the direct excitation of coherent nanosecond-pulsed high-frequency acoustic phonons in semiconducting doping superstructures by electromagnetic fields of the same frequency. Acoustic phonons are detected by a superconducting bolometer, with nanosecond resolution, at the appropriate time-of-flight across a (100) silicon substrate for ballistic longitudinal phonons when a silicon delta-doped doping superlattice is illuminated with grating-coupled nanosecond-pulsed 246-GHz laser radiation with an approximate power density of 1 kW/mm2. The absorbed phonon power density in the bolometer detector is estimated to be 10 μW/mm2, in ...


Performance Analysis Of Nitride Alternative Plasmonic Materials For Localized Surface Plasmon Applications, U. Guler, Gururaj V. Naik, Alexandra Boltasseva, Vladimir M. Shalaev, Alexander V. Kildishev Apr 2012

Performance Analysis Of Nitride Alternative Plasmonic Materials For Localized Surface Plasmon Applications, U. Guler, Gururaj V. Naik, Alexandra Boltasseva, Vladimir M. Shalaev, Alexander V. Kildishev

U. Guler

We consider methods to define the performance metrics for different plasmonic materials to be used in localized surface plasmon applications. Optical efficiencies are shown to be better indicators of performance as compared to approximations in the quasistatic regime. The near-field intensity efficiency, which is a generalized form of the well-known scattering efficiency, is a more flexible and useful metric for local-field enhancement applications. We also examine the evolution of the field enhancement from a particle surface to the far-field regime for spherical nanoparticles with varying radii. Titanium nitride and zirconium nitride, which were recently suggested as alternative plasmonic materials in ...


Binary Nanoparticle Dispersed Metamaterial Implementation And Characterization, Han Li Jan 2012

Binary Nanoparticle Dispersed Metamaterial Implementation And Characterization, Han Li

Han Li

No abstract provided.