Nanoscience and Nanotechnology Commons^™

Synthesis Of Ald Zinc Oxide And Thin Film Materials Optimization For Uv Photodetector Applications, Kandabara Nouhoum Tapily

Electrical & Computer Engineering Theses & Dissertations

Zinc oxide (ZnO) is a direct, wide bandgap semiconductor material. It is thermodynamically stable in the wurtzite structure at ambient temperature conditions. ZnO has very interesting optical and electrical properties and is a suitable candidate for numerous optoelectronic applications such as solar cells, LEDs and UV-photodetectors. ZnO is a naturally n-type semiconductor. Due to the lack of reproducible p-type ZnO, achieving good homojunction ZnO-based photodiodes such as UV-photodetectors remains a challenge. Meanwhile, heterojunction structures of ZnO with p-type substrates such as SiC, GaN, NiO, AlGaN, Si etc. are used; however, those heterojunction diodes suffer from low efficiencies. ZnO is an …

Manipulating Particles For Micro- And Nano-Fluidics Via Floating Electrodes And Diffusiophoresis, Sinan Eren Yalcin

Mechanical & Aerospace Engineering Theses & Dissertations

The ability to accurately control micro- and nano-particles in a liquid is fundamentally useful for many applications in biology, medicine, pharmacology, tissue engineering, and microelectronics. Therefore, first particle manipulations are experimentally studied using electrodes attached to the bottom of a straight microchannel under an imposed DC or AC electric field. In contrast to a dielectric microchannel possessing a nearly-uniform surface charge, a floating electrode is polarized under the imposed electric field.

The purpose is to create a non-uniform distribution of the induced surface charge, with a zero-net-surface charge along the floating electrode's surface. Such a field, in turn, generates an …

Direct Current Electrokinetic Particle Transport In Micro/Nano-Fluidics, Ye Ai

Mechanical & Aerospace Engineering Theses & Dissertations

Electrokinetics has been widely used to propel and manipulate particles in micro/nano-fluidics. The first part of this dissertation focuses on numerical and experimental studies of direct current (DC) electrokinetic particle transport in microfluidics, with emphasis on dielectrophoretic (DEP) effect. Especially, the electrokinetic transports of spherical particles in a converging-diverging microchannel and an L-shaped microchannel, and cylindrical algal cells in a straight microchannel have been numerically and experimentally studied. The numerical predictions are in quantitative agreement with our own and other researchers' experimental results. It has been demonstrated that the DC DEP effect, neglected in existing numerical models, plays an important …

Distributed Negf Algorithms For The Simulation Of Nanoelectronic Devices With Scattering, Stephen Cauley, Mathieu Luisier, Venkataramanan Balakrishnan, Gerhard Klimeck, Cheng-Kok Koh

Birck and NCN Publications

Through the Non-Equilibrium Green’s Function (NEGF) formalism, quantum- scale device simulation can be performed with the inclusion of electron-phonon scattering. However, the simulation of realistically sized devices under the NEGF formalism typically requires prohibitive amounts of memory and computation time. Two of the most demanding computational problems for NEGF simulation involve mathematical operations with structured matrices called semiseparable matrices. In this work, we present parallel approaches for these computational problems which allow for efficient distribution of both memory and computation based upon the underlying device structure. This is critical when simulating realistically sized devices due to the aforementioned computational burdens. …

Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck

Birck and NCN Publications

Ultra-thin-body (UTB) channel materials of a few nanometers in thickness are currently considered as candidates for future electronic, thermoelectric, and optoelectronic applications. Among the features that they possess, which make them attractive for such applications, their confinement length scale, transport direction, and confining surface orientation serve as degrees of freedom for engineering their electronic properties. This work presents a comprehensive study of hole velocities in p-type UTB films of widths from 15 nm down to 3 nm. Various transport and surface orientations are considered. The atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used for the electronic structure, and a semiclassical ballistic model …

Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck, Hans Kosina

Other Nanotechnology Publications

Ultra-thin-body (UTB) channel materials of a few nanometers in thickness are currently considered as candidates for future electronic, thermoelectric, and optoelectronic applications. Among the features that they possess, which make them attractive for such applications, their confinement length scale, transport direction, and confining surface orientation serve as degrees of freedom for engineering their electronic properties. This work presents a comprehensive study of hole velocities in p-type UTB films of widths from 15 nm down to 3 nm. Various transport and surface orientations are considered. The atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used for the electronic structure, and a semiclassical ballistic model …

Atomistic Study Of Electronic Structure Of Pbse Nanowires, Abhijeet Paul, Gerhard Klimeck

Birck and NCN Publications

Lead Selenide (PbSe) is an attractive ‘IV-VI’ semiconductor material to design optical sensors, lasers and thermoelectric devices. Improved fabrication of PbSe nanowires (NWs) enables the utilization of low dimensional quantum effects. The effect of cross-section size (W) and channel orientation on the bandstructure of PbSe NWs is studied using an 18 band sp3d5 tight-binding theory. The bandgap increases almost with the inverse of the W for all the orientations indicating a weak symmetry dependence. [111] and [110] NWs show higher ballistic conductance for the conduction and valence band compared to [100] NWs due to the significant splitting of the projected …

Atomistic Study Of Electronic Structure Of Pbse Nanowires, Abhijeet Paul, Gerhard Klimeck

Birck and NCN Publications

Lead Selenide (PbSe) is an attractive ‘IV-VI’ semiconductor material to design optical sensors, lasers and thermoelectric devices. Improved fabrication of PbSe nanowires (NWs) enables the utilization of low dimensional quantum effects. The effect of cross-section size (W) and channel orientation on the bandstructure of PbSe NWs is studied using an 18 band sp3d5 tight-binding theory. The bandgap increases almost with the inverse of the W for all the orientations indicating a weak symmetry dependence. [111] and [110] NWs show higher ballistic conductance for the conduction and valence band compared to [100] NWs due to the significant splitting of the projected …

Polarity Effects In The X-Ray Photoemission Of Zno And Other Wurtzite Semiconductors, M. W. Allen, Dmitry Zemlyanov, G.I.N. Waterhouse, J. B. Metson, T. D. Veal, C. F. Mcconville, S. M. Durbin

Birck and NCN Publications

Significant polarity-related effects were observed in the near-surface atomic composition and valence band electronic structure of ZnO single crystals, investigated by x-ray photoemission spectroscopy using both Al K(alpha) (1486.6 eV) and synchrotron radiation (150 to 1486 eV). In particular, photoemission from the lowest binding energy valence band states was found to be significantly more intense on the Zn-polar face compared to the O-polar face. This is a consistent effect that can be used as a simple, nondestructive indicator of crystallographic polarity in ZnO and other wurtzite semiconductors. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3562308]

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

Physics Faculty Research

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 …

Coherent Electron Transport By Adiabatic Passage In An Imperfect Donor Chain, Rajib Rahman, Richard P. Muller, James E. Levy, Malcolm S. Carroll, Gerhard Klimeck, Andrew D. Greentree, Lloyd C. L. Hollenberg

Birck and NCN Publications

Coherent tunneling adiabatic passage 􏰀CTAP􏰁 has been proposed as a long-range physical quantum bits 􏰀qubit􏰁 transport mechanism in solid-state quantum computing architectures. Although the mechanism can be implemented in either a chain of quantum dots or donors, a one-dimensional chain of donors in Si is of particular interest due to the natural confining potential of donors that can, in principle, help reduce the gate densities in solid-state quantum computing architectures. Using detailed atomistic modeling, we investigate CTAP in a more realistic triple donor system in the presence of inevitable fabrication imperfections. In particular, we investigate how an adiabatic pathway for …

Effects Of Gate-Last And Gate-First Process On Deep Submicron Inversion-Mode Ingaas N-Channel Metal-Oxide-Semiconductor Field Effect Transistors, J. J. Gu, Y. Q. Wu, Peide D. Ye

Birck and NCN Publications

Recently, encouraging progress has been made on surface-channel inversion-mode In-rich InGaAs NMOSFETs with superior drive current, high transconductance and minuscule gate leakage, using atomic layer deposited (ALD) high-k dielectrics. Although gate-last process is favorable for high-k/III-V integration, high-speed logic devices require a self-aligned gate-first process for reducing the parasitic resistance and overlap capacitance. On the other hand, a gate-first process usually requires higher thermal budget and may degrade the III-V device performance. In this paper, we systematically investigate the thermal budget of gate-last and gate-first process for deep-submicron InGaAs MOSFETs. We conclude that the thermal instability of (NH(4))(2)S as the …

Chemical Response Of Lithiated Graphite With Deuterium Irradiation, C. N. Taylor, B. Heim, Jean Paul Allain

Birck and NCN Publications

Lithium wall conditioning has been found to enhance plasma performance for graphite walled fusion devices such as TFTR, CDX-U, T-11M, TJ-II and NSTX. Among observed plasma enhancements is a reduction in edge density and reduced deuterium recycling. The mechanism by which lithiated graphite retains deuterium is largely unknown. Under controlled laboratory conditions, X-ray photoelectron spectroscopy (XPS) is used to observe the chemical changes that occur on ATJ graphite after lithium deposition. The chemical state of lithiated graphite is found to change upon deuterium irradiation indicating the formation Li-O-D, manifest at 532.9 +/- 0.6 eV. Lithium-deuterium interactions are also manifest in …

Accurate Six-Band Nearest-Neighbor Tight-Binding Model For The Π-Bands Of Bulk Graphene And Graphene Nanoribbons, Timothy B. Boykin, Mathieu Luisier, Gerhard Klimeck, Xueping Jiang, Neerav Kharche, Yu Zhou, Saroj K. Nayak

Birck and NCN Publications

Accurate modeling of the ␣-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional theory (DFT) – based calculations as well as to those based on the many-body Green’s function and screened-exchange (GW) formalism, giving excellent agreement with the ab initio AGNR bands. …

A Titanium-Supported Nanoporous Pd Electrocatalyst For Methanol Oxidation, Feng-Juan Niu, Qing-Feng Yi

Journal of Electrochemistry

Titanium-supported nanoporous palladium electrode(nanoPd /Ti) was prepared by a hydrothermal process in the presence of the ligand EDTA and using formaldehyde as reducing agent.SEM images showed that the size of Pd particles was about 60 nm and the Pd particles were connected with each other to form a three-dimensional network structure.Cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) were applied to evaluate the electrocatalytic activity of the nanoPd/Ti electrode towards methanol oxidation in alkaline solution.CV results showed that the nanoPd /Ti electrode presented high anodic peak densities and a low onset potential for methanol oxidation.Also nanoPd /Ti electrode showed excellent CO tolerance …

Electrocatalytic Oxidation Of Hydrazine At Rutin Carbon Nanotubes Modified Electrode, Hong-Fang Zhang, Qing-Lin Sheng, Jian-Bin Zheng

Journal of Electrochemistry

The electrochemical behavior and electrocatalytic oxidation of hydrazine on rutin multiwall carbon nanotubes modified glassy carbon electrode were studied by cyclic voltammetry.The experimental results indicated that the electrode exhibits good electrocatalytic activity to hydrazine at a reduced oxidation potential of 262 mV.The amperometric response of the modified electrode showed linear increase after successive addition of hydrazine in the concentration range of 2.5×10^-6~1.0×10^-4 mol·L-1 with a detection limit of 5×10^-7 mol·L^-1.

Applications Of Raman Spectroscopy Technique In Lithium Ion Batteries, Liang Zhao, Yong-Sheng Hu, Hong Li, Zhao-Xiang Wang, Hong-Xing Xu, Xue-Jie Huang, Li-Quan Chen

Journal of Electrochemistry

The Raman spectroscopy has been widely used in the study of lithium ion batteries.In this short review,we gave some examples of the applications of Raman spectroscopy in the study of electrode materials including carbonaceous materials,spinel LiM_xMn_2-x O₄,LiFePO₄,as well as polymer electrolytes,room temperaturemolten salt electrolytes and the solid-electrolyte interphase layers.The advantages and disadvantages of the ex-situ and in-situ Raman spectrum techniques are discussed.Using new Raman techniques to investigate Li-ion batteries are suggested.

Surface-Enhanced Raman Imaging Of Intracellular Bioreduction Of Chromate In Shewanella Oneidensis, Sandeep P. Ravindranath, Kristene Henne, Dorothea Thompson, Joseph Irudayaraj

Birck and NCN Publications

This proposed research aims to use novel nanoparticle sensors and spectroscopic tools constituting surface-enhanced Raman spectroscopy (SERS) and Fluorescence Lifetime imaging (FLIM) to study intracellular chemical activities within single bioremediating microorganism. The grand challenge is to develop a mechanistic understanding of chromate reduction and localization by the remediating bacterium Shewanella oneidensis MR-1 by chemical and lifetime imaging. MR-1 has attracted wide interest from the research community because of its potential in reducing multiple chemical and metallic electron acceptors. While several biomolecular approaches to decode microbial reduction mechanisms exist, there is a considerable gap in the availability of sensor platforms to …

The Composite Materials Manufacturaing Hub - Crowd Sourcing As The Norm, R. Byron Pipes, Gerhard Klimeck, Mark R. Pipes

Birck and NCN Publications

The Composites Manufacturing HUB puts compo- sites manufacturing simulations in the hands of those who need them to invent new and innovative ways to capture the extraordinary benefits of these high perfor- mance products at an acceptable manufactured cost. The HUB provides the user simple browser access to power- ful tools that simulate the actual steps and outcome con- ditions of a complex manufacturing process without the need to download and maintain software in the conven- tional manner. Learning use of the manufacturing simu- lation tools will also be accomplished on the HUB in or- der to allow for continuous …

Interface Trap Density Metrology From Sub-Threshold Transport In Highly Scaled Undoped Si N-Finfets, Abhijeet Paul, Giuseppe C. Tettamanz, Sunhee Lee, Saumitra R. Mehrotra, Nadine Collaert, Serge Biesemans, Sven Rogge, Gerhard Klimeck

Birck and NCN Publications

Channel conductance measurements can be used as a tool to study thermally activated electron transport in the sub-threshold region of state-of-art FinFETs. Together with theoretical Tight- Binding (TB) calculations, this technique can be used to understand the evolution of source-to- channel barrier height (Eb) and of active channel area (S) with gate bias (Vgs). The quantitative difference between experimental and theoretical values that we observe can be attributed to the interface traps present in these FinFETs. Therefore, based on the difference between measured and calculated values of (i) S and (ii) |∂Eb/∂Vgs| (channel to gate coupling), two new methods of …