Nanoscience and Nanotechnology Commons^™

Computing Entries Of The Inverse Of A Sparse Matrix Using The Find Algorithm, S Li, Gerhard Klimeck, E Darve

Gerhard Klimeck

An accurate and efficient algorithm, called fast inverse using nested dissection (FIND). for computing non-equilibrium Green's functions (NEGF) for nanoscale transistors has been developed and applied in the simulation of a novel dual-gate metal-oxide-semi conductor field-effect transistor (MOSFET) device structure. The method is based on the algorithm of nested dissection. A graph of the matrix is constructed and decomposed using a tree structure. An upward and downward traversal of the tree yields significant performance improvements for both the speed and memory requirements, compared to the current state-of-the-art recursive methods for NEGF. This algorithm is quite general and can be applied …

Atomistic Full-Band Simulations Of Silicon Nanowire Transistors: Effects Of Electron-Phonon Scattering, Mathieu Luisier, Gerhard Klimeck

Gerhard Klimeck

An atomistic full-band quantum transport simulator has been developed to study three-dimensional Si nanowire field-effect transistors in the presence of electron-phonon scattering. The nonequilibrium Green's function (NEGF) formalism is solved in a nearest-neighbor sp(3)d(5)s* tight-binding basis. The scattering self-energies are derived in the self-consistent Born approximation to inelastically couple the full electron and phonon energy spectra. The band dispersion and the eigenmodes of the confined phonons are calculated using a dynamical matrix that includes the bond and the angle deformations of the nanowires. The optimization of the numerical algorithms and the parallelization of the NEGF scheme enable the investigation of …

Atomistic Modeling Of The Phonon Dispersion And Lattice Properties Of Free-Standing <100> Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck

Gerhard Klimeck

Phonon dispersions in ⟨100⟩ silicon nanowires (SiNW) are modeled using a Modified Valence Force Field (MVFF) method based on atomistic force constants. The model replicates the bulk Si phonon dispersion very well. In SiNWs, apart from four acoustic like branches, a lot of flat branches appear indicating strong phonon confinement in these nanowires and strongly affecting their lattice properties. The sound velocity (Vsnd) and the lattice thermal conductance (κl) decrease as the wire cross-section size is reduced whereas the specific heat (Cv) increases due to increased phonon confinement and surface-to-volume ratio (SVR).

Spectroscopy Of A Deterministic Single-Donor Device In Silicon, M. Fuechsle, J. A. Miwa, S. Mahapatra, H. Ryu, S. Lee, O. Warschkow, L. C. L. Hollenberg, G. Klimeck, M. Y. Simmons

Gerhard Klimeck

We present a single electron transistor (SET) based on an individual phosphorus dopant atom in an epitaxial silicon environment. Using scanning tunneling microscope (STM) hydrogen lithography, the single impurity is deterministically placed with a spatial accuracy of ±1 lattice site within a donor-based transport device. Low temperature transport measurements confirm the presence of the single donor and show that the donor charge state can be precisely controlled via gate voltages. We observe a charging energy that is remarkably similar to the value expected for isolated P donors in bulk silicon, which is in sharp contrast to previous experiments on single-dopant …

Strain Effects On The Phonon Thermal Properties Of Ultra-Scaled Si Nanowires, Abhijeet Paul, Gerhard Klimeck

Gerhard Klimeck

The impact of uniaxial and hydrostatic stress on the ballistic thermal conductance (jl) and the specific heat (Cv) of [100] and [110] Si nanowires are explored using a Modified Valence Force Field phonon model. An anisotropic behavior of jl and isotropic nature of Cv under strain are predicted for the two wire orientations. Compressive (tensile) strain decreases (increases) Cv. The Cv trend with strain is controlled by the high energy phonon sub-bands. Dominant contribution of the low/mid (low/high) energy bands in [100] ([110]) wire and their variation under strain governs thebehaviorofjl.VC 2011AmericanInstituteofPhysics.

Rate Equations For The Phonon Peak In Resonant-Tunneling Structures, Roger Lake, Gerhard Klimeck, J. P. Anantram, Supriyo Datta

Gerhard Klimeck

The ratio of the phonon peak current to the main peak current in double-barrier resonant-tunneling structures is significantly enhanced by barrier asymmetry. Previously, using the Keldysh formalism, we derived analytical expressions, valid in the zero-temperature, high-bias regime, which explained this eftect. We now provide analytical expressions valid for finite temperature and bias obtained from (i) an intuitive derivation using a rate equation approach and (ii) a more general derivation using the Keldysh formalism. The results of the two difFerent approaches are shown to be essentially identical for the ex- perimental device parameters. The finite temperature expressions shed light on the …

Transport-Based Dopant Metrology In Advanced Finfets, Gabriel P. Lansbergen, Rajib Rahman, Cameron J. Wellard, Jaap Caro, Nadine Collaert, Serge Biesemans, Gerhard Klimeck, Lloyd C. L. Hollenberg, Sven Rogge

Gerhard Klimeck

Ultra-scaled FinFET transistors bear unique fingerprint-like device-to-device differences attributed to random single impurities. Through correlation of experimental data with multimillion atom simulations in NEMO 3-D, we can identify the impurity’s chemical species and determine their concentration, local electric field and depth below the Si/SiO2 interface. The ability to model the excited states rather than just the ground states is the critical need. We therefore demonstrate a new approach to atomistic impurity metrology and confirm the assumption of tunneling through individual impurity quantum states.

Design Guidelines For True Green Leds And High Efficiency Photovoltaics Using Znse/Gaas Digital Alloys, Samarth Agarwal, Kyle H. Montgomery, Timothy B. Boykin, Gerhard Klimeck, Jerry M. Woodall

Gerhard Klimeck

In the fields of solid state lighting and high efficiency solar photovoltaics (PV), a need still exists for a material system that can target the 2.3-2.5eV energy range. The ZnSe/GaAs system is shown to have great potential. The digital alloy approach can be utilized as a well-ordered design alternative to the disordered alloy systems. The effective band-gap of the ZnSe/GaAs(001) superlattice has been studied, as a function of the constituent monolayers using tight binding. The possibility of engineering a range of band-gaps with the same material system, to achieve the optimum value for solar PV and LED applications, has been …

Real-Time Biosensor For The Assessment Of Nanotoxicity And Cancer Electrotherapy, Evangelia Hondroulis

FIU Electronic Theses and Dissertations

Knowledge of cell electronics has led to their integration to medicine either by physically interfacing electronic devices with biological systems or by using electronics for both detection and characterization of biological materials. In this dissertation, an electrical impedance sensor (EIS) was used to measure the electrode surface impedance changes from cell samples of human and environmental toxicity of nanoscale materials in 2D and 3D cell culture models. The impedimetric response of human lung fibroblasts and rainbow trout gill epithelial cells when exposed to various nanomaterials was tested to determine their kinetic effects towards the cells and to demonstrate the biosensor’s …

Nitroxide-Functionalized Graphene Oxide From Graphite Oxide, Yazmin I. Avila-Vega, Cesar C. Leyva-Porras, Marcela Mireles, Manuel Quevedo-Lopez, Javier Macossay-Torres, Jose Bonilla-Cruz

Chemistry Faculty Publications and Presentations

A facile method for preparing functionalized graphene oxide single layers with nitroxide groups is reported herein. Highly oxidized graphite oxide (GO=90.6%) was obtained, slightly modifying an improved Hummer’s method. Oxoammonium salts (OS) were investigated to introduce nitroxide groups to GO, resulting in a one-step functionalization and exfoliation. The mechanisms of functionalization/exfoliation are proposed, where the oxidation of aromatic alcohols to ketone groups, and the formation of alkoxyamine species are suggested. Two kinds of functionalized graphene oxide layers (GOFT1 and GOFT2) were obtained by controlling the amount of OS added. GOFT1 and GOFT2 exhibited a high interlayer spacing (d0001 = 1.12nm), …

Scalar Differential Equation For Slowly-Varying Thickness-Shear Modes In At-Cut Quartz Resonators With Surface Impedance For Acoustic Wave Sensor Application, Huijing He, Jiashi Yang, John A. Kosinski

Department of Mechanical and Materials Engineering: Faculty Publications

For time-harmonic motions, we generalize a 2-D scalar differential equation derived previously by Tiersten for slowly-varying thickness-shear vibrations of AT-cut quartz resonators. The purpose of the generalization is to include the effects of surface acoustic impedance from, e.g., mass layers or fluids for sensor applications. In addition to the variation of fields along the plate thickness, which is considered in the usual 1-D acoustic wave sensor models, the equation obtained also describes in-plane variations of the fields, and therefore can be used to study the vibrations of finite plate sensors with edge effects. The equation is compared with the theory …

An Investigation Of Thin Films Formed On Zinc By Spectroscopic Ellipsometry, Juan Zuo, Ying Chen, Chang-Jian Lin, Andreas Erbe

Journal of Electrochemistry

The formation of natural oxide films on polycrystalline zinc surface, the growth of natural oxide films in different atmospheres, as well as the electrochemical process of metal zinc in alkaline carbonate solution, studied recently by using spectroscopic ellipsometry in our group, are introduced. The objective of this paper is to outline that the optical, electrical properties, the change and growth kinetics of zinc metal oxide film on the surface can be investigated by in-situ and ex-situ ellipsometry, which makes significant sense to evaluate the overall performance of zinc oxide layer.

Synthesis Of Pani/Nihcf Nanocomposite Particles And Eqcm Measurement Of Ion Exchange Properties In Solutions Containing Cd2+, Yu-Jiao Yang, Xiao-Gang Hao, Xu-Li Ma, Zhong-De Wang, Zhong-Lin Zhang, Nian-Chen Han

Journal of Electrochemistry

The PANI/NiHCF nanocomposite particles were synthesized on the CNTs-modified Pt substrate by one-step co-polymerization using cyclic voltammetry. Electrochemical quartz crystal microbalance (EQCM) technique was adopted to investigate the polymerization process of the nanocomposite particles and the mechanism of ion exchange in aqueous solution containing Cd²⁺． The morphology and structure of the as-prepared composite particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). Combined with cyclic voltammetry (CV) and energy dispersive spectroscopy (EDS), the electrochemical behavior and the mechanism of ion exchange were also investigated in electrolytes of Cd^{2+ …}

Applications Of Spectroscopic Ellipsometry In Corrosion Investigation, Ling-Jie Li, Yu-Ling He, Jing-Lei Lei, Sheng Tao Zhang

Journal of Electrochemistry

As a highly-sensitive and non-destructive in situ technique, spectroscopic ellipsometry has been widely applied in corrosion investigation to acquire the dynamic information of the “electrode-medium” interface during corrosion. This paper lays out some representative demonstrations in several established optical models used to interpret data obtained with spectroscopic ellipsometry in corrosion investigation. In addition, the latest trends in development of this technique are analyzed.

Elementary Studies Of Twisted Bilayer Graphene, Branden P. Burns, Yong P. Chen

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the nanotechnology field, some existing materials and applications are harmful to the environment, not efficient for certain tasks, or too expensive to be fully utilized. Graphene is a strong and cheap material that can be used to improve current nanotechnologies for more practical uses in society. Twisted bilayer graphene (TBG) is an orientation of graphene layers that exhibit different properties than regular bilayer graphene. It is made by placing a single layer of graphene on top of another at an angle with respect to the other lattice orientation. Understanding the characteristics of TBG is important to uncover more physics …

Thin Electrical Double Layer Simulation Of Micro-Electrochemical Supercapacitors, Kaitlyn Fisher, Guoping Xiong, Timothy S. Fisher

The Summer Undergraduate Research Fellowship (SURF) Symposium

The deteriorating state of the environment has drawn many people to hybrid electric vehicles. Electrochemical micro-supercapacitors are of interest in this field because of their high power density relative to other micro-power sources. However, little is known about how the properties of the electrolyte used affect the performance of such devices. The first step of this investigation was to use thermoreflectance microscopy to measure the temperature change of the electrodes while charging and discharging supercapacitor samples. The components of these samples were graphitic petal electrodes with a Ti/Au covering (for enhanced light reflectance) on a SiO₂ base, with a …

Prism - Materials Simulation Tool, Ryan Widjaja, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

MEMS (Micro-electromechanical System) is a combined electrical and mechanical nano-scaled device with rapidly growing applications. We have developed a contacting radio frequency capacitive MEMS that is commonly used as capacitive switches and contact actuators in PRISM (Prediction of Reliability, Integrity and Survivability of Microsystems) lab at Purdue University. Our research team has focused on creating a simulation of MEMS’s survivability towards crazing and cracking. Our particular objective in this project is to create a tool that can help users perform complex quantitative calculations regarding the properties of different materials. This tool will generate various plots visualizing the properties, such as …

Crystalline Cellulose – Atomistic Modeling Toolkit, Mateo Gomez, Pablo Zavattieri Dr.

The Summer Undergraduate Research Fellowship (SURF) Symposium

Nature has created efficient strategies to make materials with hierarchical internal structure that often exhibit exceptional mechanical properties. One such example is found in cellulose, in fact it is eight times stronger than stainless steel and advantage is that cellulose incredibly cheap, because processing is obtained from purified wood pulp (it is environmental friendly). The most prevalent modeling technique to study the fundamental mechanical behavior of the crystalline cellulose has been Molecular Dynamics (MD). As a predictive tool, MD allows us to study the behavior of crystalline cellulose at the atomic level, and as such, it accurately predicts the crystalline …

Phase-Field Dislocation Dynamics Code Optimization, Jaime A. Perez, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

The importance of the study of nanocrystalline materials has gained a huge amount of attention these years due to its extraordinary mechanical, electrical and chemical properties. One significant way to progress in this field is by simulating the behavior of the particles in nano scale, which is not only a need but a challenge due to massive interactions that occur there. The phase-field dislocation dynamics (PFDD) method has been successfully employed in the modeling of plastic deformation, creep and grain boundary sliding. In PFDD, the plastic strain and the energy are functions of phase fields that obey a set of …

Dna Based Carbon Nanotube Porphyrin Nanohybrids Molecular Recognization And Regeneration, Molly M. Riccitelli, Hanyu Zhang, Jong Hyun Choi

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the search to improve solar cells, scientists are exploring new materials that will provide better current transfer. One material that has emerged as a strong contender is the single walled carbon nanotube (SWNT). Current DNA-SWNT based films combined with chromophores have poor operational lifetimes compared to commercial solar cells. Once exposed to light the chromophore begins to degrade, eventually rendering the solar cell unusable. To solve this problem, we used a method involving multiple steps. First we found which DNA sequences formed structures around the SWNT that could hold the most chromophores by using a spectrophotometer to test the …

Synthesis And Characterization Of Nucleic Acid-Functionalized Nanomaterials, Brianna S. Carroll, Jong Hyun Choi

The Summer Undergraduate Research Fellowship (SURF) Symposium

Motor proteins such as kinesin move along microtubules in order to transport cellular cargos throughout the cell by obtaining energy from RNA hydrolysis which allows the cell to complete the tasks needed to stay alive. In this work, we developed synthetic molecular motors using DNA enzymes (DNAzyme) and fluorescent nanomaterials which mimic the functions and structures of motor proteins. A DNAzyme-capped CdS nanoparticle and a RNA-functionalized single-walled carbon nanotube (SWCNT) were used as a walker and a track in the motor platform, respectively. As a walking mechanism, the DNAzyme cleaved the RNA substrates in the presence of metal cations. The …

Synthesizing Bismuth Telluride Nanowires In A Large Scale And Investigating The Energy Filtering Effect By Blending Bismuth Telluride Nanowires And Silver Nanoparticle In Thermoelectrics, Henka Darsono, Haiyu Fang, Yue Wu

The Summer Undergraduate Research Fellowship (SURF) Symposium

More than 50% of the energy sources becomes “waste” energy generally dissipated to the atmosphere in the form of heat. Thermoelectric effect is a conversion of temperature difference to electric voltage and can be used to convert the wasted heat to useful work. Nanomaterials have great potentials in the field of thermoelectric effect since they have properties that can allow higher efficiency in converting this wasted heat to electricity as compared to bulk materials. The purpose of this project is to develop a method to synthesize bismuth telluride (Bi₂Te₃) nanowires on a large scale and incorporate …

Assessing The Mvs Model For Nanotransistors, Siyang Liu, Xingshu Sun, Mark S. Lundstrom

The Summer Undergraduate Research Fellowship (SURF) Symposium

A simple semi-empirical compact MOSFET model has been developed, which is called MIT virtual source (MVS) model. Compare to other model used in industry, MVS model requires only a few parameters, most of which can be directly obtained from experiment, and produce accurate results. One aim of this paper is to test the applicability of the MVS model to transistor made from MoS₂ rather than silicon. Another target is to determine the sustainability of the MVS model under different transistor tests. To achieve these goals, the MVS model will be used to fit the experimental data on MoS_{2 …}

Pulsed Laser Coating Of Bioceramic (Hap) And Niti Nanoparticles On Metallic Implants, Aayush Goswami, Gary J. Cheng

The Summer Undergraduate Research Fellowship (SURF) Symposium

This research deals with increasing the biocompatibility of the bio implants which have a global market valued more than $94.1 billion . The surface of the metal alloys used for the bone implants need to be coated with bio compatible materials like HAp(Hydroxyapatite), graphene, etc. in order to promote the growth of cells(osteoblasts) on the surface of the implants. Various techniques like plasma spray coating, ion beam sputter coating, etc. have been used before to coat such materials on a substrate, however these have faced problems of coating quality. In order to perfect this coating, that is make it more …

Real-Time Substrate Transport Control For Stable And Efficient Thin-Film-Based Roll-To-Roll (R2r) Micro-Nanomanufacturing, Wencheng Wang, Guoao Sun, Liang Pan

The Summer Undergraduate Research Fellowship (SURF) Symposium

The commercialization of electronic devices requires the high efficiency and stable mirco-nanomanufacturing processes that allow frequent design upgrades. R2R Nano is a gateway to science and engineering research that aims to impact the widespread adoption of R2R technologies for low-cost, high-volume production of high technology products on flexible substrates. However, there are lots of the mechanical and chemical factors influencing the system performance when fabricating nano-scale structures. Thus, feedback control system is increasingly playing a great role in improving the R2R performance.

The aim of the project is to design a feedback control system for enhancing the performance of the …

Developing A Crystal Viewer Tool For Nanohub, Osiris V. Ntarugera, Gerhard Klimeck

The Summer Undergraduate Research Fellowship (SURF) Symposium

Most materials found in nature have their atoms arranged in a regular and repeated pattern known as crystalline structure; this is particularly true for metals. It is very important to understand the crystal structure of materials in order to predict their properties such as the electric conductivity, heat transfer, and more. Particularly, students and scholars in the field of material science need a way to visualize the different crystal structures. Atomic structures of elements are not visible to the naked eye. In that context, a computer based tool can be used to simulate and to visualize the crystal structures of …

Microfluidic Platform For Immobilizing Cells To Surfaces, Sze Yung Li, Arvind Raman

The Summer Undergraduate Research Fellowship (SURF) Symposium

Atomic Force Microscope (AFM) is an advanced nanotechnology tool for image mapping and cell properties measuring. One of the major challenges presented to the scientists in the field is the procedure for sample preparation. In order for a cell or virus to be measured by the AFM, it has to be firmly attached to the surface. Existing methods including chemical functionalization of surface for cells binding are often very slow process which hinders the possibility of high throughput measurement. Therefore, we propose a new method that utilizes a fluid circulation system to immobilize cells of interest to designated area to …

Mechanical Design Of Real-Time Substrate Transport Control For Stable And Efficient Thin-Film-Based Roll-To-Roll (R2r) Micro-Nanomanufacturing, Guoao Sun, Liang Pan

The Summer Undergraduate Research Fellowship (SURF) Symposium

The commercialization of electronic devices requires the high efficiency and stable mirco-nanomanufacturing processes that allow frequent design upgrades. R2R Nano is a gateway to science and engineering research that aims to impact the widespread adoption of R2R technologies for low-cost, high-volume production of high technology products on flexible substrates. However, there are lots of the mechanical and chemical factors influencing the system performance when fabricating nano-scale structures. Thus, feedback control system is increasingly playing a great role in improving the R2R performance.

The aim of my work of the project is more related to design mechanical section of the whole …

Shot Noise Thermometry For Thermal Characterization Of Templated Carbon Nanotubes, Robert A. Sayer, Sunkook Kim, Aaron D. Franklin, Saeed Mohammadi, Timothy Fisher

Robert A Sayer

A carbon nanotube (CNT) thermometer that operates on the principles of electrical shot noise is reported. Shot noise thermometry is a self-calibrating measurement technique that relates statistical fluctuations in dc current across a device to temperature. A structure consisting of vertical, top, and bottom-contacted single-walled carbon nanotubes in a porous anodic alumina template was fabricated and used to measure shot noise. Frequencies between 60 and 100 kHz were observed to preclude significant influence from 1/f noise, which does not contain thermally relevant information. Because isothermal models do not accurately reproduce the observed noise trends, a self-heating shot noise model has …

Toward Surround Gates On Vertical Single-Walled Carbon Nanotube Devices, Aaron D. Franklin, Robert A. Sayer, Timothy D. Sands, Timothy Fisher, David B. Janes

Robert A Sayer

The one-dimensional, cylindrical nature of single-walled carbon nanotubes (SWCNTs) suggests that the ideal gating geometry for nanotube field-effect transistors (FETs) is a surround gate (SG). Using vertical SWCNTs templated in porous anodic alumina, SGs are formed using top-down processes for the dielectric/metal depositions and definition of the channel length. Surround gates allow aggressive scaling of the channel to 25% of the length attainable with a bottom-gate geometry without incurring short-channel effects. The process demonstrated here for forming SGs on vertical SWCNTs is amenable for large-scale fabrication of multinanotube FETs.