Nanoscience and Nanotechnology Commons^™

An All-Silicon Passive Optical Diode, Li Fan, Jian Wang, Leo T. Varghese, Hao Shen, Ben Niu, Yi Xuan, Andrew M. Weiner, Minghao Qi

Birck and NCN Publications

A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input power is higher than the forward input. The silicon optical diode is ultracompact and is compatible with current complementary metal-oxide semiconductor processing.

Size Effects In Niti From Density Functional Theory Calculations, Karthik Guda Vishnu, Alejandro Strachan

Birck and NCN Publications

We use density functional theory to characterize how size affects the relative stability of thin NiTi slabs of different crystal structures and its implication on the martensitic phase transition that governs shape memory. We calculate the surface energies of B2' phase (austenite), B19 (orthorhombic), B19' (martensite), and a body-centered orthorhombic phase, the theoretically predicted ground state. We find that (110)(B2) surfaces with in-plane atomic displacements stabilize the austenite phase with respect to B19' and BCO; thus, slabs with such orientations are predicted to exhibit a decrease in martensite transition temperature with decreasing thickness. Our calculations predict a critical thickness of …

Resolving Structure And Mechanical Properties At The Nanoscale Of Viruses With Frequency Modulation Atomic Force Microscopy, David Martinez-Martin, Carolina Carrasco, Mercedes Hernando-Perez, Pedro J. De Pablo, Julio Gomez-Herrero, Rebeca Perez, Mauricio G. Mateu, Jose L. Carrascosa, Daniel Kiracofe, John Melcher, Arvind Raman

Birck and NCN Publications

Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images …

Energy-Based Yield Criterion For Pmma From Large-Scale Molecular Dynamics Simulations, Eugenio Jaramillo, Nathaniel Wilson, Stephen Christensen, Jonathan Gosse, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics (MD) with the DREIDING force field to characterize the ultimate mechanical response of amorphous poly(methyl methacrylate). We characterize how volumetric and deviatoric strains contribute to yield for a wide range of loading conditions from pure deviatoric, volume-conserving cases to isotropic volume expansion. We propose and apply an energy-based yield criterion to define yield consistently for all cases. Our results show that permanent deformation occurs when either the deviatoric or volumetric strains reach critical values, except in a narrow region around the transformation between deviatoric- and volumetric-dominated yield where the two strain invariants interact. In contrast, the …

Optimization Of Power And Efficiency Of Thermoelectric Devices With Asymmetric Thermal Contacts, Kazuaki Yazawa, Ali Shakouri

Birck and NCN Publications

We report the theoretical efficiency of thermoelectric power generation with asymmetric thermal contacts to reservoirs. A key ingredient is the electrical and thermal co-optimization. Generic formula of the maximum power output and the optimum leg length are obtained. The Curzon-Ahlborn limit at maximum power can be rigorously derived when the dimensionless figure-of-merit is very large for any asymmetric thermal contact resistances. The results differ from cyclic thermodynamic engines, and some of the reasons are discussed. We also point out the similarity and differences with single-level quantum dot heat engines, which assume no explicit thermal contact resistance with reservoirs. (C) 2012 …

Computational Study Of Energy Filtering Effects In One-Dimensional Composite Nano-Structures, Raseong Kim, Mark S. Lundstrom

Birck and NCN Publications

Possibilities to improve the Seebeck coefficient S versus electrical conductance G trade-off of diffusive composite nano-structures are explored using an electro-thermal simulation framework based on the non-equilibrium Green's function method for quantum electron transport and the lattice heat diffusion equation. We examine the role of the grain size d, potential barrier height Phi(B), grain doping, and the lattice thermal conductivity kappa(L) using a one-dimensional model structure. For a uniform kappa(L), simulation results show that the power factor of a composite structure may be improved over bulk with the optimum Phi(B) being about k(B)T, where k(B) and T are the Boltzmann …

Quantum-Hall Plateau-Plateau Transition In Top-Gated Epitaxial Graphene Grown On Sic (0001), T. Shen, A. T. Neal, M. L. Bolen, Jiangjiang Gu, L. W. Engel, Michael A. Capano, Peide D. Ye

Birck and NCN Publications

We investigate the low-temperature magneto-transport properties of monolayer epitaxial graphene films formed on the Si-face of semi-insulating 4H SiC substrates by a high-temperature sublimation process. A high-k top-gate on the epitaxial graphene is realized by inserting a fully oxidized nanometer-thin aluminum film as a seeding layer, followed by an atomic layer deposition process. At low temperatures, the devices demonstrate a strong field effect by the top gate with an on/off ratio of similar to 7 and an electron mobility up to similar to 3250 cm(2)/Vs. After the observation of the half-integer quantum-Hall effect for monolayer epitaxial graphene films, detailed magneto-transport …

Laser Direct Growth Of Graphene On Silicon Substrate, Dapeng Wei, Xianfan Xu

Birck and NCN Publications

We demonstrate laser direct growth of few layer graphene on a silicon substrate. In our study, a continuous wave laser beam was focused on a poly(methyl methacrylate) (PMMA)-coated silicon wafer to evaporate PMMA and melt the silicon wafer. Carbon atoms, decomposed from PMMA, were absorbed by the molten silicon surface, and then separated from silicon in the cooling process to form few-layer graphene. This Si-catalyzed method will provide a new approach and platform for applications of graphene. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675636]

Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

The impacts of the two-beam interference heating on the number of core-shell and embedded nanoparticles and on nanostructure coarsening are studied numerically based on the non-linear dynamical model for dewetting of the pulsed-laser irradiated, thin (< 20 nm) metallic bilayers. The model incorporates thermocapillary forces and disjoining pressures, and assumes dewetting from the optically transparent substrate atop of the reflective support layer, which results in the complicated dependence of light reflectivity and absorption on the thicknesses of the layers. Stabilizing thermocapillary effect is due to the local thickness-dependent, steady- state temperature profile in the liquid, which is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Linear stability analysis of the model equations set for Ag/Co bilayer predicts the dewetting length scales in the qualitative agreement with experiment.

Metal Chalcogenide Nanoparticle Gel Networks: Their Formation Mechanism And Application For Novel Material Generation And Heavy Metal Remediation Via Cation Exchange Reactions, Irina Ramona Pala

Wayne State University Dissertations

METAL CHALCOGENIDE NANOPARTICLE GEL NETWORKS: THEIR FROMATION MECHANISM AND APPLICATION FOR NOVEL MATERIAL GENERATION AND HEAVY METAL REMEDIATION VIA CATION EXCHANGE REACTIONS

by

IRINA R. PALA

February 2012

Advisor: Dr. Stephanie L. Brock

Major: Chemistry

Degree: Doctor of Philosophy

The dissertation research is focused on (1) uncovering the mechanism of metal chalcogenide nanoparticle gel formation; (2) extending the cation exchange reaction protocol to zinc sulfide gel networks, with the goal of accessing new aerogel chemistries and understanding the factors that drive the process; and (3) conducting a quantitative analysis of the ability of ZnS aerogels to remove heavy metal ions …

Method For Increasing The Efficiency Of Organic Photovoltaic Cells, Jinsong Huang, Yongbo Yuan

Department of Mechanical and Materials Engineering: Faculty Publications

The present invention is directed to an organic photovoltaic cell that contains one or more dipole regions generally disposed between an organic active region and the electrodes and a process for producing such an organic photovoltaic cell.

Cell Permeabilization And Inhibition Of Voltage-Gated Ca²+ And Na+ Channel Currents By Nanosecond Pulsed Electric Fields, Vasyl Nesin, Angela M. Bowman, Shu Xiao, Andrei G. Pakhomov

Bioelectrics Publications

Previous studies have found that nanosecond pulsed electric field (nsPEF) exposure causes long-term permeabilization of the cell plasma membrane. In this study, we utilized the whole-cell patch-clamp method to study the nsPEF effect on currents of voltage-gated (VG) Ca²⁺ and Na⁺ channels (I_Ca and I_Na) in cultured GH3 and NG108 cells. We found that a single 300 or 600 ns pulse at or above 1.5-2 kV/cm caused prolonged inhibition of I_Ca and I_Na. Concurrently, nsPEF increased a non-inactivating leak current (I_leak), presumably due to the formation of nanoelectropores or larger …

Gaining Insight Into The Physics Of Dynamic Atomic Force Microscopy In Complex Environments Using The Veda Simulator, Daniel Kiracofe, John Melcher, Arvind Raman

Birck and NCN Publications

Dynamic atomic force microscopy (dAFM) continues to grow in popularity among scientists in many different fields, and research on new methods and operating modes continues to expand the resolution, capabilities, and types of samples that can be studied. But many promising increases in capability are accompanied by increases in complexity. Indeed, interpreting modern dAFM data can be challenging, especially on complicated material systems, or in liquid environments where the behavior is often contrary to what is known in air or vacuum environments. Mathematical simulations have proven to be an effective tool in providing physical insight into these non-intuitive systems. In …

Full Band Atomistic Modeling Of Homo-Junction Ingaas Band-To-Band Tunneling Diodes Including Band Gap Narrowing, Woo-Suhl Cho, Mathieu Luisier, Dheeraj Mohata, Suman Datta, David Pawlik, Sean L. Rommel, Gerhard Klimeck

Birck and NCN Publications

A homo-junction In0.53Ga0.47As tunneling diode is investigated using full-band, atomistic quantum transport approach based on a tight-binding model (TB) and the Non-equilibrium Green’s Function formalism. Band gap narrowing (BGN) is included in TB by altering its parameters using the Jain-Roulston model. BGN is found to be critical in the determination of the current peak and the second turn-on in the forward bias region. An empirical excess current that mimics additional recombination paths must be added to the calculation to model the diode behavior in the valley current region. Overall the presented model reproduces experimental data well.

Feasibility, Accuracy, And Performance Of Contact Block Reduction Method For Multi-Band Simulations Of Ballistic Quantum Transport, Hoon Ryu, Hong-Hyun Park, Mincheol Shin, Dragica Vasileska, Gerhard Klimeck

Birck and NCN Publications

Numerical utilities of the contact block reduction (CBR) method in evaluating the retarded Green’s function are discussed for 3D multi-band open systems that are represented by the atomic tight-binding (TB) and continuum k * p (KP) band model. It is shown that the methodology to approximate solutions of open systems, which has been already reported for the single-band effective mass model, cannot be directly used for atomic TB systems, since the use of a set of zinc blende crystal grids makes the inter-coupling matrix non-invertible. We derive and test an alternative with which the CBR method can be still practical …

Nanoprobe I-V Characterization Of Cdte/Cds Micro And Nano-Patterned Solar Cells, Heber Prieto

Open Access Theses & Dissertations

This thesis presents a novel way to characterize micro and nano patterned cadmium telluride thin film solar cells via a nano-probe system. A historical review of CdTe-based solar cells is presented first followed by review of the technology developed to produce the patterned CdTe cells. A detailed presentation is then provided on the use of a Zyvex nanoprobing system to characterize the patterned solar cells. The I-V response of micro- and nano-patterned solar cells stimulated under different e-beam conditions is presented and analyzed. Suggestions of how to improve the technique are provided. This work documents, for the first time, the …

Graphene Stuctures For Energy Storage Application, Mohammad Arif Ishtiaque Shuvo

Open Access Theses & Dissertations

Energy storage devices are receiving extensive attention in recent years due to the increasing demand of energy. Super-capacitor is one of the energy storage devices with high specific power density and wide applications in electronic vehicles, commercial mobile electronics, and military devices. Carbon based materials are widely used in making Electrochemical Double Layer Capacitor (EDLC) or super-capacitor for their excellent porous nature along with their electron transport capability. By increasing the specific surface area of the porous carbon materials, specific capacitance of the super-capacitor can be significantly improved. Graphene, a newly discovered material, has been incorporated in making super-capacitor electrodes …

Macro And Microfluidic Flows For Skeletal Regenerative Medicine, Brandon D. Riehl, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

Fluid flow has a great potential as a cell stimulatory tool for skeletal regenerative medicine, because fluid flow-induced bone cell mechanotransduction in vivo plays a critical role in maintaining healthy bone homeostasis. Applications of fluid flow for skeletal regenerative medicine are reviewed at macro and microscale. Macroflow in two dimensions (2D), in which flow velocity varies along the normal direction to the flow, has explored molecular mechanisms of bone forming cell mechanotransduction responsible for flow-regulated differentiation, mineralized matrix deposition, and stem cell osteogenesis. Though 2D flow set-ups are useful for mechanistic studies due to easiness in in situ and post-flow …

Polymeric Nanocarriers For The Regional And Systemic Delivery Of Therapeutics To And Through The Lungs, Balaji Bharatwaj

Wayne State University Dissertations

The lungs are considered as one of the fastest portals of entry to the bloodstream and oral inhalation (OI) has long been accepted as the preferred mode of administration of therapeutics to the respiratory tract. However, despite its advantages, the lungs have been largely underutilized to target ailments not only of systemic relevance but also several other grave conditions including lung cancer and tuberculosis. Polymeric nanocarriers (PNCs) have several advantages over other drug delivery vehicles including sustained release of moieties, ease of cellular internalization and improved targeting, and hence hold the promise to greatly augment the potential of OI therapies. …

Sacrificial Structure Preforms For Thin Part Machining, Scott Smith, Robert Wilhelm, Brian Dutterer, Harish Cherukuri, Gaurav Goel

Department of Mechanical and Materials Engineering: Faculty Publications

Thin parts are often difficult to create by machining because they have insufficient static and dynamic stiffness. Accurate thin parts are difficult to achieve due to clamping forces, cutting forces, residual stresses, and chatter. Sacrificial structure preforms support the part during machining, but they are not part of the finished component. Preforms may be created in many ways, including forging, welding, gluing, casting, or additive processes. They can be used in many workpiece materials including metals, polymers, and ceramics. We describe a novel process that uses sacrificial structures to make machining insensitive to the thinness of finished parts.