Nanoscience and Nanotechnology Commons^™

Modeling Of Subcontinuum Thermal Transport Across Semiconductor-Gas Interfaces, Druv Singh, Xiaohui Guo, Alina Alexeenko, Jayathi Y. Murthy, Timothy Fisher

Birck and NCN Publications

A physically rigorous computational algorithm is developed and applied to calculate subcontinuum thermal transport in structures containing semiconductor-gas interfaces. The solution is based on a finite volume discretization of the Boltzmann equation for gas molecules (in the gas phase) and phonons (in the semiconductor). A partial equilibrium is assumed between gas molecules and phonons at the interface of the two media, and the degree of this equilibrium is determined by the accommodation coefficients of gas molecules and phonons on either side of the interface. Energy balance is imposed to obtain a value of the interface temperature. The classic problem of …

Squeeze-Film Damping Of Flexible Microcantilevers At Low Ambient Pressures: Theory And Experiment, Jin Lee, Ryan C. Tung, Arvind Raman, Hartono Sumali, John Sullivan

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

An improved theoretical approach is proposed to predict the dynamic behavior of long, slender and flexible microcantilevers affected by squeeze-film damping at low ambient pressures. Our approach extends recent continuum gas damping models (Veijola 2004 J. Micromech. Microeng. 14 1109–18, Gallis and Torczynski 2004 J. Microelectromech. Syst. 13 653–9), which were originally derived for a rigid oscillating plate near a wall, to flexible microcantilevers for calculating and predicting squeeze-film damping ratios of higher order bending modes at reduced ambient pressures. Theoretical frequency response functions are derived for a flexible microcantilever beam excited both inertially and via external forcing. Experiments performed …

Tunable Magnetic Response Of Metamaterials, Shumin Xiao, Uday K. Chettiar, Alexander V. Kildishev, V. Drachev, I C. Khoo, V. M. Shalaev

Birck and NCN Publications

We demonstrate a thermally tunable optical metamaterial with negative permeability working in the visible range. By covering coupled metallic nanostrips with aligned nematic liquid crystals (NLCs), the magnetic response wavelength of the metamaterial is effectively tuned through control of the ambient temperature, changing the refractive index of LC via phase transitions. By increasing the ambient temperature from 20 to 50 degrees C, the magnetic response wavelength shifts from 650 to 632 nm. Numerical simulations confirm our tests and match the experimental observations well.

Translation Of Nanoantenna Hot Spots By A Metal-Dielectric Composite Superlens, Zhengtong Liu, Mark D. Thoreson, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We employ numerical simulations to show that highly localized, enhanced electromagnetic fields, also known as "hot spots," produced by a periodic array of silver nanoantennas can be spatially translated to the other side of a metal-dielectric composite superlens. The proposed translation of the hot spots enables surface-enhanced optical spectroscopy without the undesirable contact of molecules with metal, and thus it broadens and reinforces the potential applications of sensing based on field-enhanced fluorescence and surface-enhanced Raman scattering.

Translation Of Nanoantenna Hot Spots By A Metal-Dielectric Composite Superlens, Zhengtong Liu, Mark D. Thoreson, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We employ numerical simulations to show that highly localized, enhanced electromagnetic fields, also known as "hot spots," produced by a periodic array of silver nanoantennas can be spatially translated to the other side of a metal-dielectric composite superlens. The proposed translation of the hot spots enables surface-enhanced optical spectroscopy without the undesirable contact of molecules with metal, and thus it broadens and reinforces the potential applications of sensing based on field-enhanced fluorescence and surface-enhanced Raman scattering.

Vertical Carbon Nanotube Devices With Nanoscale Lengths Controlled Without Lithography, Aaron D. Franklin, Robert A. Sayer, Timothy D. Sands, David B. Janes, Timothy S. Fisher

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

Vertical single-walled carbon nanotubes (vSWCNTs) are synthesized within highly ordered porous anodic alumina (PAA) templates supported on Si substrates. A process for obtaining thin-film PAA with long-range ordered nanopores is presented in this paper. Each nanopore contains at most one v-SWCNT that is supported by a dielectric and addressed by electrochemically formed Pd nanowire source contacts and evaporated Pd drain contacts. Characteristics of these completely vertical, two-terminal nanotube devices are presented. Control of the v-SWCNT length is demonstrated using a straightforward etching process with lengths of less than 100 nm achieved without the need for complex/expensive lithography. This effective nanoscale …

Simplified Model For Periodic Nanoantennae: Linear Model And Inverse Design, Joshua Borneman, Kuo-Ping Chen, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We determine and use a minimal set of numerical simulations to create a simplified model for the spectral response of nanoantennae with respect to their geometric and modeling parameters. The simplified model is then used to rapidly obtain best-fit modeling parameters to match experimental results, accurately predict the spectral response for various geometries, and inversely design antennae to have a desired performance. This method is structure and model independent, and is applied here to both nanoantenna pair arrays and strips modeled using a 3D finite-element method and 2D spatial harmonic analysis, respectively. Typical numerical simulations may need hours per model, …

Ultrasensitive Protein Detection In Blood Serum Using Gold Nanoparticle Probes By Single Molecule Spectroscopy, Jiji Chen, Chungang Wang, Joseph Irudayaraj

Birck and NCN Publications

A one-step rapid and ultrasensitive immunoassay capable of detecting proteins in blood serum is developed using gold nanoprobes and fluorescence correlation spectroscopy (FCS). In this approach we take advantage of the inherent photoluminescence property of gold nanoparticles (GNPs) to develop a fluorophore-free assay to observe binding entities by monitoring the diffusion of bound versus unbound molecules in a limited confocal volume. 40-nm GNPs conjugated separately with rabbit anti-IgG (Fc) and goat anti-IgG (Fab) when incubated in blood serum containing IgG forms a sandwich structure constituting dimers and oligomers that can be differentiated by to detect IgG in blood serum at …

Pseudomorphic Stabilization Of Rocksalt Gan In Tin/Gan Multilayers And Superlattices, Vijay Rawat, Dmitri Zakharov, E A. Stach, Timothy D. Sands

Birck and NCN Publications

Gallium nitride (GaN) in its stable wurtzite phase has proven its utility in light-emitting diodes and diode lasers as well as high-temperature and high-power electronic devices. In addition to its equilibrium wurtzite phase, GaN exhibits two cubic polymorphs, a zinc-blende phase and a high-pressure rocksalt phase. Here, we report the pseudomorphic stabilization of the high-pressure rocksalt phase of GaN within TiN/GaN multilayers as verified using x-ray diffraction and high-resolution transmission electron microscopy. High-resolution lattice imaging confirmed that the lattice parameter of the rocksalt GaN phase is 0.41 nm. The critical thickness of the GaN film that can be pseudomophically stabilized …

Metamaterial Devices For The Terahertz Band, Gabriel Paul Kniffin

Center for Electron Microscopy and Nanofabrication Publications and Presentations

Terahertz (THz) and metamaterials are both hot topics in electromagnetics research. The THz band (0.1-10 THz) lies in the ‘gap’ between microwave and far infrared regions. Research is currently underway to characterize how these waves interact with matter, with potential applications including security screening, medical imaging, and non-destructive evaluation. Metamaterials are artificial materials containing sub-wavelength structures whose material properties, μ and ǫ can be ‘tuned’ to desired specifications, including simultaneously negative values, resulting in exotic properties such as a negative refractive index. Current metamaterials research includes the design of devices that operate at THz frequencies, filling a niche left wide …

Flexible Electronics Using Ion Implantation To Adhere Polymer Substrate To Single Crystal Silicon Substrate, Terry L. Alford, Douglas C. Thompson Jr., Hyunchul Kim, Michael A. Nastasi, James W. Mayer, Daniel Adams

Department of Mechanical and Materials Engineering: Faculty Publications

An electronic apparatus uses a single crystalline silicon Substrate disposed adjacent to a flexible substrate. The electronic apparatus may be a flexible flat panel display, or a flexible printed circuit board. The flexible substrate can be made from polymer, plastic, paper, flexible glass, and stainless steel. The flexible substrate is bonded to the single crystalline substrate using an ion implantation process. The ion implantation process involves the use of a noble gas Such as hydrogen, helium, Xenon, and krypton. A plurality of semiconductor devices are formed on the single crystalline silicon Substrate. The semi conductor devices may be thin film …

Temperature Dependence Of Hot-Carrier Relaxation In Pbse Nanocrystals: An Ab Initio Study, Hua Bao, Bradley F. Habenicht, Oleg V. Prezhdo, X Ruan

Birck and NCN Publications

Temperature-dependent dynamics of phonon-assisted relaxation of hot carriers, both electrons and holes, is studied in a PbSe nanocrystal using ab initio time-domain density-functional theory. The electronic structure is first calculated, showing that the hole states are denser than the electron states. Fourier transforms of the time-resolved energy levels show that the hot carriers couple to both acoustic and optical phonons. At higher temperature, more phonon modes in the high-frequency range participate in the relaxation process due to their increased occupation number. The phonon-assisted hot-carrier relaxation time is predicted using nonadiabatic molecular dynamics, and the results clearly show a temperature-activation behavior. …

Thermal Conductivity Of Bismuth Telluride Nanowire Array-Epoxy Composite, Kalapi G. Biswas, Timothy D. Sands, Baratunde Cola, Xianfan Xu

Birck and NCN Publications

Electrodeposition of nanowire array in porous anodic alumina (PAA) templates combine the performance benefits offered by crystallographic texture control, lattice thermal conductivity suppression through boundary scattering of phonons, elastic relaxation of misfit strain, and scalablity essential for high efficiency thermoelectric devices. The template material, however, can serve as a thermal shunt thereby reducing the effective thermoelectric performance. Here, we demonstrate a process of minimizing the parasitic thermal conduction by replacing the PAA matrix with SU-8 (kappa similar to 0.2 W/m K). We report a reduction in the performance penalty from 27% for Bi2Te3/PAA to similar to 5% for Bi2Te3/SU-8 nanocomposite …

Demonstration Of Quadrature-Squeezed Surface Plasmons In A Gold Waveguide, Alexander Huck, Stephan Smolka, Peter Lodahl, Anders S. Sorensen, Alexandra Boltasseva, Jiri Janousek, Ulrik Andersen

Birck and NCN Publications

We report on the efficient generation, propagation, and reemission of squeezed long-range surface-plasmon polaritons in a gold waveguide. Squeezed light is used to excite the nonclassical surface-plasmon polaritons, and the reemitted quantum state is fully characterized by complete quantum tomographic reconstruction of the density matrix. We find that the plasmon-assisted transmission of nonclassical light in metallic waveguides can be described by a beam splitter relation. This result is explained theoretically.

Performance Analysis Of Statistical Samples Of Graphene Nanoribbon Tunneling Transistors With Line Edge Roughness, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Using a three-dimensional, atomistic quantum transport simulator based on the tight-binding method, we investigate statistical samples of single-gate graphene nanoribbon (GNR) tunneling field-effect transistors (TFETs) with different line edge roughness probabilities. We find that as the nanoribbon edges become rougher, the device OFF-current drastically increases due to a reduction of the graphene band gap and an enhancement of source-to-drain tunneling leakage through the gate potential barrier. At the same time, the ON-current remains almost constant. This leads to a deterioration of the transistor subthreshold slopes and to unacceptably low ON/OFF current ratios limiting the switching performances of GNR TFETs.

Demonstration Of Quadrature-Squeezed Surface Plasmons In A Gold Waveguide, Alexander Huck, Stephan Smolka, Peter Lodahl, Anders S. Sorensen, Alexandra Boltasseva, Jiri Janousek, Ulrik Andersen

Birck and NCN Publications

We report on the efficient generation, propagation, and reemission of squeezed long-range surface-plasmon polaritons in a gold waveguide. Squeezed light is used to excite the nonclassical surface-plasmon polaritons, and the reemitted quantum state is fully characterized by complete quantum tomographic reconstruction of the density matrix. We find that the plasmon-assisted transmission of nonclassical light in metallic waveguides can be described by a beam splitter relation. This result is explained theoretically.

Anisotropic Metamaterials Emulated By Tapered Waveguides: Application To Optical Cloaking, Igor I. Smolyaninov, Vera N. Smolyaninova, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We demonstrate that metamaterial devices requiring anisotropic dielectric permittivity and magnetic permeability may be emulated by specially designed tapered waveguides. This approach leads to low-loss, broadband performance. Based on this technique, we demonstrate broadband electromagnetic cloaking in the visible frequency range on a scale similar to 100 times larger than the wavelength.

Influence Of Nano-Al2O3 Particles In Nickel Electro-Crystallization Process, Cheng-Yu Tan, Wei Hu, Hang Cui, Yu Liu

Journal of Electrochemistry

The influence of nano-Al₂O₃ particles in nickel electro-deposition on copper matrix from acid sulphate solution was studied under various potentials by using cyclic voltammetry(CV) and chronoamperometry(CA).The results show that the beginning potential of electro-deposition was about-740 mV(vs.SCE) for Ni-Al₂O₃ solution system.With the step-potential moving to the negative direction,the nucleation time of electro-deposition for Ni-Al₂O₃ solution system was shortened gradually.Compared with that of pure Ni deposition system,the nucleation time tm,corresponding to the peak current of Ni-Al₂O₃ deposition system was apparently shortened under the lower step-potential:-740~-830 mV,which indicates that Al …

Metal-Oxide-Semiconductor Field-Effect Transistors On Gaas (111)A Surface With Atomic-Layer-Deposited Al2o3 As Gate Dielectrics, Xu M, Y Q. Wu, O Koybasi, T Shen, P. D. Ye

Birck and NCN Publications

GaAs inversion-mode metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic-layer-deposited Al2O3 as gate dielectrics are fabricated on (111)A and (100) surfaces. With the same channel length of 0.75 mu m, the maximum drain current of 15 mA/mm on n-channel MOSFET is obtained on (111)A surface, in great contrast to only 1 mu A/mm on (100) surface. For p-channel MOSFETs, maximum drain currents of 0.17 mA/mm and 0.8 mA/mm are obtained on (111)A and (100) surfaces, respectively. An empirical model is proposed to correlate the experimental observation with the existing III-V MOS theories.

Device Considerations For Development Of Conductance-Based Biosensors, Kangho Lee, Pradeep R. Nair, Adina Scott, Muhammad A. Alam, David B. Janes

Birck and NCN Publications

Design and fabrication of electronic biosensors based on field-effect-transistor (FET) devices require understanding of interactions between semiconductor surfaces and organic biomolecules. From this perspective, we review practical considerations for electronic biosensors with emphasis on molecular passivation effects on FET device characteristics upon immobilization of organic molecules and an electrostatic model for FET-based biosensors.

High Efficiency Excitation Of Plasmonic Waveguides With Vertically Integrated Resonant Bowtie Apertures, Edward C. Kinzel, Xianfan Xu

Birck and NCN Publications

In recent years, many nanophotonic devices have been developed. Much attention has been given to the waveguides carrying surface plasmon polariton modes with subwavelength confinement and long propagation length. However, coupling far field light into a nano structure is a significant challenge. In this work, we present an architecture that enables high efficiency excitation of nanoscale waveguides in the direction normal to the waveguide. Our approach employs a bowtie aperture to provide both field confinement and high transmission efficiency. More than six times the power incident on the open area of the bowtie aperture can be coupled into the waveguide. …

Resonant Oscillation Of Misch-Metal Atoms In Filled Skutterudites, Yaguo Wang, Xianfan Xu, Jihui Yang

Birck and NCN Publications

We investigate vibrational behaviors in misch-metal filled antimony skutterudites in the time domain. At higher filling ratios of guest atoms, the vibration frequency approaches that of the cage structure and the amplitude becomes stronger. Furthermore, the reduction of lattice thermal conductivity over a wide temperature range can be explained using the measured resonant vibrational frequency. These findings reveal that the reduction of the lattice thermal conductivity is a result of scattering of acoustic phonons due to the resonant interaction between guest atoms and lattice phonons.

Real Space First-Principles Derived Semiempirical Pseudopotentials Applied To Tunneling Magnetoresistance, Kirk Huw Bevan, Tony Low, H Guo

Birck and NCN Publications

We present a real space density functional theory localized basis set semiempirical pseudopotential (SEP) approach. The method is applied to iron and magnesium oxide, where bulk SEP and local spin density approximation band structure calculations are shown to agree within approximately 0.1 eV. Subsequently we investigate the qualitative transferability of bulk derived SEPs to Fe/MgO/Fe tunnel junctions. We find that the SEP method is particularly well suited to address the tight binding transferability problem because the transferability error at the interface can be characterized not only in orbital space (via the interface local density of states) but also in real …

Rarefied Gas Flow In Microtubes At Different Inlet-Outlet Pressure Ratios, Z Yang, Suresh Garimella

Birck and NCN Publications

A model is developed for rarefied gas flow in long microtubes with different inlet-outlet pressure ratios at low Mach numbers. The model accounts for significant changes in Knudsen number along the length of the tube and is therefore applicable to gas flow in long tubes encountering different flow regimes along the flow length. Predictions from the model show good agreement with experimental measurements of mass flow rate, pressure drop, and inferred streamwise pressure distribution obtained under different flow conditions and offer a better match with experiments than do those from a conventional slip flow model.

Automated Crystal Phase And Orientation Mapping Of Nanocrystals In A Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov, Edgar F. Rauch, Stavros Nicolopoulos

Physics Faculty Publications and Presentations

An automated technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is described. It is based on the projected reciprocal lattice geometry that is extracted from electron diffraction spot patterns. The required hardware allows for a scanning‐precession movement of the primary electron beam on the crystalline sample and can be interfaced to any newer or older TEM. The software that goes with this hardware is flexible in its intake of raw data so that it can also create orientation and phase maps of nanocrystal from high resolution TEM (HRTEM) images. When the nanocrystals possess …

Modulated Nanopores Using Pulse Anodization On Thin Aluminum, Mahesh Babu Gunukula

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nanoporous anodic aluminum oxide has traditionally been made in one of two ways: "Mild Anodization (MA)" or "Hard Anodization (HA)". The former method produces self-ordered pore structures but it is slow and only works for a narrow range of processing conditions; the latter method, which is widely used in the aluminum industry, is faster but it produces films with disordered pore structures. Here we report a novel approach termed "pulse anodization" that combines the advantages of the MA and HA processes. By designing the pulse sequences it is possible to control both the composition and pore structure of the anodic …

Magnetic Sensors For Biodetection, Pranjali Vineet Sneha Deshpande

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of thesis is to design magnetic sensor for detection of nanoparticles. Recently integrating the standard laboratory techniques into integrated system on chip is growing attention. Recent development is to combine magnetic markers and magnetoresistive sensors together in magnetic chip. In this thesis two magnetoresistive sensors were studied and designed.

By applying magnetic fields, magnetic nanoparticles can be manipulated on-chip, which can be utilized to pull the molecules to specific binding sites or to test the binding strength and distinguish between specifically and non-specifically bound molecules

Magnetoresistive sensors are compatible with the semiconductor industry which provides electronic signal directly …

Efficient Unidirectional Ridge Excitation Of Surface Plasmons, I P. Radko, S I. Bozhevolnyi, G Brucoli, L Mart´In-Moreno, F J. Garc´Ia-Vidal, A Boltasseva

Birck and NCN Publications

Using leakage-radiation microscopy, we characterize the efficiency of unidirectional surface-plasmon excitation with periodic (800 nm) arrays of 130-nm-high and 330-nm-wide gold ridges on a thin gold film illuminated with a focused (5-mu m-wide) laser beam. We demonstrate that, at the resonant wavelength of 816 nm, the excitation efficiency of > 0.4 can be obtained with >= 5 ridges by adjusting the beam position. Conducting numerical simulations, we account for the experimental results and calculate the electric-field enhancement achieved near the gold surface.

Unified Theory Of Gas Damping Of Flexible Microcantilevers At Low Ambient Pressures, Rahul Bidkar, Ryan Tung, Alina Alexeenko, Sumali Hartono, Arvind Raman

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

Predicting the gas damping of microcantilevers oscillating in different vibration modes in unbounded gas at low pressures is relevant for increasing the sensitivity of microcantilever-based sensors. While existing free-molecular theories are valid only at very high Knudsen numbers, continuum models are valid only at very low Knudsen numbers. We solve the quasisteady Boltzmann equation and compute a closed-form fit for gas damping of rectangular microcantilevers that is valid over four orders of magnitude of Knudsen numbers spanning the free-molecular, the transition, and the low pressure slip flow regimes. Experiments are performed using silicon microcantilevers under controlled pressures to validate the …

Reflection Contributions To The Dispersion Artefact In Ftir Spectra Of Single Biological Cells, Paul Bassan, Hugh Byrne, Joe Lee, Franck Bonnier, Colin Clarke, Paul Dumas, Ehsan Gazi, Michael Brown, Noel Clarke, Peter Gardner

Articles

Fourier transform infrared spectra of a single cell in transflection geometry are seen to vary significantly with position on the cell, showing a distorted derivative-like lineshape in the region of the optically dense nucleus. A similar behaviour is observable in a model system of the protein albumin doped in a potassium bromide disk. It is demonstrated that the spectrum at any point is a weighted sum of the sample reflection and transmission and that the dominance of the reflection spectrum in optically dense regions can account for some of the spectral distortions previously attributed to dispersion artefacts. Rather than being …