Nanoscience and Nanotechnology Commons^™

Numerical Modeling Of Plasmonic Nanoantennas With Realistic 3d Roughness And Distortion, Alexander V. Kildishev, Joshua D. Borneman, Kuo-Ping Chen, Vladimir P. Drachev

Birck and NCN Publications

Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement factor that should be involved in their design. Herein we aim to treat roughness by introducing a realistic roughened geometry into the finite element (FE) model. Even if the roughness does not result in significant loss, it does result in a spectral shift and inhomogeneous broadening of the resonance, which could be critical when fitting the FE simulations …

Structure And Optical Properties Of Self-Assembled Multicomponent Plasmonic Nanogels, Tao Cong, Satvik N. Wani, Peter Anthony Paynter, Radhakrishna Sureshkumar

Biomedical and Chemical Engineering - All Scholarship

Multicomponent plasmonic nanogels (PNGs) capable of broadband absorption of light in the 400-700 nm wavelength range were synthesized by the self-assembly of metal nanoparticles with wormlike surfactant micelles. Small angle x-ray scattering and rheological experiments suggest that the nanoparticles bridge micelle fragments to aid the formation a stable gel phase with exceptional color uniformity. Their optical absorbance could be robustly tuned by changing the nanoparticle type (Au/Ag), size, shape, and/or concentration. The PNGs have relatively low viscosity and are thermoreversible. Potential applications to the manufacturing of coatings and interfaces for solar energy harvesting and reconfigurable optical devices can be envisioned.

Using Nanotechnology To Detect Nerve Agents, Mark N. Goltz, Dong-Shik Kim, Leeann Racz

Faculty Publications

Nanotechnology has opened a wide range of opportunities having potential impacts in areas as diverse as medicine and consumer products. In collaboration with researchers at the University of Toledo UT, Air Force Institute of Technology AFIT scientists are exploring the possibility of using a nanoscale organic matrix to detect organophosphate OP nerve agents. Current techniques for detecting OP compounds are expensive and time consuming. Developing a nanoscale organic matrix sensor would allow for direct, real-time sensing under field conditions. This article describes the science behind such a sensor and its possible applications. High-performance sensors are needed to protect Soldiers and …

Ultrafast Electron Diffraction Study Of The Dynamics Of Antimony Thin Films And Nanoparticles, Mahmoud Abdel-Fattah

Electrical & Computer Engineering Theses & Dissertations

The ultrafast fast phenomena that take place following the application of a 120 fs laser pulse on 20 nm antimony thin films and 40 nm nanoparticles were studied using time-resolved electron diffraction. Samples are prepared by thermal evaporation, at small thickness (< 10 nm) antimony nanoparticles form while at larger thicknesses we get continuous thin films.

The samples are annealed and studied by static heating to determine their Debye temperatures, which were considerably less than the standard value. The thermal expansion under static heating also yielded the expansion coefficient of the sample material. Nanoparticle samples gave a very accurate thermal expansion coefficient (11 × 10^-6 K^-1).

Ultrafast time resolved electron diffraction …

Scattering Mechanisms In A High-Mobility Low-Density Carbon-Doped (100) Gaas Two-Dimensional Hole System, J. D. Watson, S. Mondal, G. A. Csathy, M. J. Manfra, E. H. Hwang, S. Das Sarma, L. N. Pfeiffer, K. W. West

Birck and NCN Publications

We report on a systematic study of the density dependence of mobility in a low-density carbon-doped (100) GaAs two-dimensional hole system (2DHS). At T = 50 mK, a mobility of 2.6 x 10(6) cm(2)/Vs at a density p = 6.2 x 10(10)cm(-2) was measured. This is the highest mobility reported for a 2DHS to date. Using a backgated sample geometry, the density dependence of mobility was studied from 2.8 x 10(10) cm(-2) to 1 x 10(11) cm(-2). The mobility vs density cannot be fit to a power law dependence of the form alpha similar to p(alpha) using a single exponent …

Supersymmetry Identifies Molecular Stark States Whose Eigenproperties Can Be Obtained Analytically, Mikhail Lemeshko, Mustafa Mustafa, Sabre Kais, Bretislav Friedrich

Birck and NCN Publications

We made use of supersymmetric (SUSY) quantum mechanics to find the condition under which the Stark effect problem for a polar and polarizable closed-shell diatomic molecule subjected to collinear electrostatic and nonresonant radiative fields becomes exactly solvable. The condition Delta omega = omega(2)/4(m+1)(2) connects values of the dimensionless parameters omega and Delta omega that characterize the strengths of the permanent and induced dipole interactions of the molecule with the respective fields. The exact solutions are obtained for the vertical bar(J) over tilde = m, m; omega, Delta omega > family of 'stretched' states. The field-free and strong-field limits of the combined-fields …

Room Temperature Device Performance Of Electrodeposited Insb Nanowire Field Effect Transistors, Suprem Das, Collin J. Delker, Dmitri Zakharov, Yong P. Chen, Timothy D. Sands, David B. Janes

Birck and NCN Publications

InSb nanowires have been formed by electrodeposition in porous anodic alumina templates and employed as transistor channels. The 100 nm diameter nanowires had a zinc blende crystal structure. Single-nanowire field-effect transistors (NW-FETs) with a channel length of 500 nm exhibited on-currents of similar to 40 mu A, on/off ratios of similar to 16-20, drain conductances of similar to 71 mu S and field-effect electron mobility of similar to 1200 cm(2) V(-1) s(-1). Compared with reported NW-FETs, the on-current is large and the current saturation occurs at low source-drain voltages. These characteristics can be understood in terms of velocity saturation effects …

Dynamics Of Entanglement In A Two-Dimensional Spin System, Qing Xu, Gehad Sadiek, Sabre Kais

Birck and NCN Publications

We consider the time evolution of entanglement in a finite two-dimensional transverse Ising model. The model consists of a set of seven localized spin-1/2 particles in a two-dimensional triangular lattice coupled through nearest-neighbor exchange interaction in the presence of an external time-dependent magnetic field. The magnetic field is applied in different function forms: step, exponential, hyperbolic, and periodic. We found that the time evolution of the entanglement shows an ergodic behavior under the effect of the time-dependent magnetic fields. Also, we found that while the step magnetic field causes great disturbance to the system, creating rapid oscillations, the system shows …

The Design And Manufacture Of A Microfluidic Reactor For Synthesis Of Cadmium Selenide Quantum Dots Using Silicon And Glass Substrates, Peter Gonsalves

Materials Engineering

A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of silicon and Pyrex glass. Microfabrication techniques were used to etch the channels into the silicon wafer. Holes were wet-drilled into Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was aligned to the etched silicon wafer and both were anodically bonded to complete the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350^oC under 5.46N of force.  Bulk CdSe solution was mixed at room temperature and treated as a single injection. The syringe containing …

Comparison Of Photothermal And Piezoacoustic Excitation Methods For Frequency And Phase Modulation Atomic Force Microscopy In Liquid Environments, A. Labuda, K. Kobayashi, Daniel Kiracofe, K. Suzuki, P. H. Gruetter, H. Yamada

Birck and NCN Publications

In attempting to perform frequency modulation atomic force microscopy (FM-AFM) in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM) which lies in between phase modulation atomic force microscopy (PM-AFM) and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard FM-AFM theory no longer applies. Although our recovery procedure applies to all cantilever excitation methods in principle, its practical implementation may be difficult, or even impossible, if the cantilever is driven piezoacoustically. …

Formation Of Silicon Nanodots Via Ion Beam Sputtering Of Ultrathin Gold Thin Film Coatings On Si, Osman El-Atwani, Sami Ortoleva, Alex Cimaroli, Jean Paul Allain

Birck and NCN Publications

Ion beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 x 10(17) cm(-2). In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide …

Improving Near-Field Confinement Of A Bowtie Aperture Using Surface Plasmon Polaritons, Pornsak Srisungsitthisunti, Okan Ersoy, Xianfan Xu

Birck and NCN Publications

Bowtie aperture is known to produce subdiffraction-limited optical spot with high intensity. In this work, we investigate integrating a bowtie aperture with circular grooves to reduce the divergence of the near-field produced by the bowtie aperture. Numerical results indicate that surface waves reflected from circular grooves improve the field confinement of a bowtie aperture along the polarization axis. These circular grooves with period near half the wavelength of surface plasmon polaritons reduce the spot size by as much as 40% at distances between 20 and 100 nm from the surface and create a more symmetrical optical spot. (C) 2011 American …

Synthesis And Catalytic Property Of Flaked Spindle-Like Cuo Nanocrystals, Jian-Feng Fan, Li-Qing Li, Yu-Feng Huang, Lou-Zhen Fan

Journal of Electrochemistry

A simple and efficient electrochemical route was developed for the synthesis of flaked spindle-like CuO nanocrystals using aqueous electrolyte and Cu sacrificial anode (graphite as the cathode) in an undivided cell at a constant potential mode under room temperature. The morphologies, structure and component of CuO nanocrystals obtained were characterized by SEM, XRD, respectively. Flaked spindle-like CuO nanocrystals were successfully used to modify a GC electrode to detect H₂O₂ with cyclic voltammetry (CV) and amperometric (AC).The results showed that products were pure monoclinic CuO nanocrystals. The linear range for the determination of hydrogen peroxide is from 1.0 …

Influence Of Tert-Butylpyridine On The Band Energetics Of Nanostructured Tio2 Electrodes And The Photoelectrochemical Properties Of Dye-Seneitized Electrodes, Shu-Ming Yang, Ji-Chao Wang, Hui-Zhi Kou, Hong-Bin Xue, Hong-Jun Wang, Yu-Ling Guo

Journal of Electrochemistry

The flat band edges (Efb) of nanostructured TiO₂ electrodes in electrolyte solutions with tert-butylpyridine (TBP) of different concentrations have been determined with spectroelectrochemical technique. TBP played a role in band energetics of nanostructured TiO₂ electrodes. The Efb values of -2.25, -2.46 and -2.62 V were determined in three 0.2 mol•L^-1 tetrabutylammonium perchlorate (TBAP) acetonitrile electrolytes which contain 0, 0.2 and 0.4 mol•L^-1 TBP respectively. The addition of Li+ ions shifted Efb positively. The Efb values of -1.12, -1.22 and -1.30 V were determined in three 0.2 mol•L^-1 LiClO₄ acetonitrile electrolytes which contain 0, 0.2 …

Dft Study Of Co2 Reduction To Hydrocarbons On Cu Surfaces, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

CO₂ reduction on Cu(111) single crystal surfaces was studied using DFT calculations on the reaction energies and the minimum energy paths. The results indicated that the possible reaction paths for CO₂ reduction on Cu(111) surface are CO₂(g) + H* → COOH* → (CO +OH)*, (CO + H)* → CHO*, CHO + H → CH₂O* → (CH_2⁺O)*, CH₂* + 2H* → CH₄ or 2CH₂* → C₂H₄. On Cu(111) surface, the reaction rate is controlled by steps of CH₂O* → (CH_{2 …}

The Flip-Flop Behavior Of Acetonitrile At Au Electrode Surface Investigated By Sum Frequency Generation Vibrational Spectroscopy, Zhi Huang, Xin Tang, Gang-Hua Deng, En-Cai Zhou, Hong-Fei Wang, Yuan Guo

Journal of Electrochemistry

The electrochemical interface between liquid acetonitrile and polycrystal gold electrode is investigated by in situ infrared visible sum frequency generation spectroscopy (SFG-VS). The structure of acetonitrile adsorbed at polycrystal gold electrode surface is studied as a function of electrode potential. The SFG spectra of CH₃ group indicate acetonitrile orients in response to the electrode potential. The SFG signal of CH₃ group turns lower as the electrode potential changes from -700mV to 300mV, and vanishes around the 300mV(pzc), then becomes a negative signal above 500mV, which indicates that the orientation is predominately with the CH₃ group toward the …

Chaos-Assisted Emission From Asymmetric Resonant Cavity Microlasers, Susumu Shinohara, Takahisa Harayama, Takehiro Fukushima, Martina Hentschel, Satoshi Sunada, Evgenii Narimanov

Birck and NCN Publications

We study emission from quasi-one-dimensional modes of an asymmetric resonant cavity that are associated with a stable periodic ray orbit confined inside the cavity by total internal reflection. It is numerically demonstrated that such modes exhibit directional emission, which is explained by chaos-assisted emission induced by dynamical tunneling. Fabricating semiconductor microlasers with an asymmetric resonant cavity, we experimentally demonstrate the selective excitation of the quasi-one-dimensional modes by employing the device structure to preferentially inject currents to these modes and observe directional emission in good accordance with the theoretical prediction based on chaos-assisted emission.

Engineered Valley-Orbit Splittings In Quantum-Confined Nanostructures In Silicon, Rajib Rahman, J. Verdujin, Neerav Kharche, Gabriel Lansbergen, Purdue University Gerhard Klimeck, Lloyd Hollenberg, Sven Rogge

Birck and NCN Publications

An important challenge in silicon quantum electronics in the few electron regime is the poten- tially small energy gap between the ground and excited orbital states in 3D quantum confined nanostructures due to the multiple valley degeneracies of the conduction band present in silicon. Understanding the “valley-orbit” (VO) gap is essential for silicon qubits, as a large VO gap prevents leakage of the qubit states into a higher dimensional Hilbert space. The VO gap varies considerably depending on quantum confinement, and can be engineered by external electric fields. In this work we investigate VO splitting experimentally and theoretically in a …

Fabrication And Realistic Modeling Of Three-Dimensional Metal-Dielectric Composites, Mark D. Thoreson, Jieran R. Fang, Alexander V. Kildishev, Ludmila J. Prokopeva, Piotr Nyga, Uday K. Chettiar, Vladimir M. Shalaev, Vladimir P. Drachev

Birck and NCN Publications

Historically, the methods used to describe the electromagnetic response of random, three-dimensional (3D), metal-dielectric composites (MDCs) have been limited to approximations such as effective-medium theories that employ easily-obtained, macroscopic parameters. Full-wave numerical simulations such as finite-difference time domain (FDTD) calculations are difficult for random MDCs due to the fact that the nanoscale geometry of a random composite is generally difficult to ascertain after fabrication. We have developed a fabrication method for creating semicontinuous metal films with arbitrary thicknesses and a modeling technique for such films using realistic geometries. We extended our two-dimensional simulation method to obtain realistic geometries of 3D …

Particle-Hole Asymmetry Of Fractional Quantum Hall States In The Second Landau Level Of A Two-Dimensional Hole System, A. Kumar, N. Samkharadze, Gabor A. Csathy, Michael J. Manfra, L. N. Pfeiffer, K. W. West

Birck and NCN Publications

We report the unambiguous observation of a fractional quantum Hall state in the Landau level of a two-dimensional-hole sample at the filling factor v = 8/3. We identified this state by a quantized Hall resistance and an activated temperature dependence of the longitudinal resistance and found an energy gap of 40 mK. Notably, the particle-hole conjugate state at filling factor v = 7/3 in our sample did not develop down to 6.9 mK. This observation is contrary to that in electron samples, in which the 7/3 state is typically more stable than the 8/3 state. We present evidence that the …