Nanoscience and Nanotechnology Commons^™

Complex Martensitic Nanostructure In Zr Nanowires: A Molecular Dynamics Study, Alexander Thompson, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics to characterize the martensitic nanostructure that develops when bcc Zr nanowires are cooled down and transform to hcp (martensite). We find that size has a strong effect on nanostructure and even very small wires (a few nanometers in diameter) exhibit complex, multidomain structures with large internal strains (up to similar to 6%). Long and thin wires result in domains coexisting along their axes while those with small aspect ratios exhibit coexistence of domains within their cross-section. We also that find regions of fcc Zr that develop to bridge neighboring hcp domains.

Scanning Tunneling Microscope Study Of Striated Carbon Ridges In Few-Layer Epitaxial Graphene Formed On 4h-Silicon Carbide (0001), Sara E. Harrison, Michael A. Capano, R. Reifenberger

Birck and NCN Publications

Atomically resolved scanning tunneling microscope images of carbon ridge defects found in few-layer graphene formed on the C-face (0001) of 4H-silicon carbide reveal a striated exterior surface formed from out-of-plane distortions of the hexagonal graphene lattice. While ridge formation is likely explained by compressive in-plane stresses coupled with the small values of the bending modulus for few-layer graphene, the striated structure along the ridges argues for a localized unidirectional stress in the material directed along the ridge length.

Charge-Pumping Characterization Of Interface Traps In Al2o3/In0.75ga0.25as Metal-Oxide-Semiconductor Field-Effect Transistors, W Wang, J. Deng, Jc M. Hwang, Y Xuan, P. D. Ye

Birck and NCN Publications

Charge pumping was used to characterize the interface traps between Al2O3 and In0.75Ga0.25As in an n-channel inversion-mode metal-oxide-semiconductor field-effect transistor (MOSFET). By analyzing the charge pumped under gate voltage pulses of different rise and fall times, the interface trap density was extracted across the band gap of In0.75Ga0.25As. The interface trap density was found to be 4x10(12) cm(-2) eV(-1) near the conduction band and to peak at 3x10(13) cm(-2) eV(-1) mid-gap. The result helps explain the promising on-state performance of the Al2O3/In0.75Ga0.25As MOSFET and the need to further improve the interface so that its off-state performance can be on par …

Exact Calculation Of Entanglement In A 19-Site Two-Dimensional Spin System, Qing Xu, Sabre Kais, Maxim Naumov, Ahmed Sameh

Birck and NCN Publications

Using the trace minimization algorithm, we carried out an exact calculation of entanglement in a 19-site two-dimensional transverse Ising model. This model consists of a set of localized spin-1/2 particles in a two-dimensional triangular lattice coupled through exchange interaction J and subject to an external magnetic field of strength h. We demonstrate, for such a class of two-dimensional magnetic systems, that entanglement can be controlled and tuned by varying the parameter lambda = h/J in the Hamiltonian and by introducing impurities into the systems. Examining the derivative of the concurrence as a function of lambda shows that the system exhibits …

Band Offsets Of Al2o3/Inxga1-Xas (X=0.53 And 0.75) And The Effects Of Postdeposition Annealing, N V. Nguyen, M Xu, O A. Kirillov, P. D. Ye, C Wang, K Cheung, J S. Suehle

Birck and NCN Publications

Band offsets at the interfaces of InxGa1-xAs/Al2O3/Al where x=0.53 and 0.75 were determined by internal photoemission and spectroscopic ellipsometry. The photoemission energy threshold at the InxGa1-xAs/Al2O3 interface was found to be insensitive to the indium composition but shifted to a lower energy after a postdeposition annealing at high temperatures. Subthreshold electron photoemission was also observed for the annealed sample and was attributed to interfacial layer formation during the annealing process.

Large-Scale Graphitic Thin Films Synthesized On Ni And Transferred To Insulators: Structural And Electronic Properties, Helin Cao, Qingkai Yu, Robert Colby, Deepak Pandey, C S. Park, Jie Lian, Dmitry Zemlyanov, Isaac Childres, V. P. Drachev, E A. Stach, Muhammad Hussain, Hao Li, Steven S. Pei, Yong P. Chen

Birck and NCN Publications

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm's have been synthesized. Structural characterizations by atomic force microscopy, scanning tunneling microscopy, cross-sectional transmission electron microscopy (XTEM), and Raman spectroscopy confirm that such large-scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few-layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth …

Fourier Transform Infrared Microspectroscopy And Multivariate Methods For Radiobiological Dosimetry, Aidan Meade, Colin Clarke, Hugh Byrne, Fiona Lyng

Articles

The scientific literature contains an ever-growing number of reports of applications of vibrational spectroscopy as a multivariate non-invasive tool for analysis of biological effects at the molecular level. Recently, Fourier transform infrared microspectroscopy (FTIRM) has been demonstrated to be sensitive to molecular events occurring in cells and tissue after exposure to ionizing radiation. In this work the application of FTIRM in the examination of dose-dependent molecular effects occurring in skin cells after exposure to ionizing radiation with the use of partial least-squares regression (PLSR) and generalized regression neural networks (GRNN) was studied. The methodology is shown to be sensitive to …

Bdf-Like Methods For Nonlinear Dynamic Analysis, S. Dong

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

We present several time integration algorithms of second-order accuracy that are numerically simple and effective for nonlinear elastodynamic problems. These algorithms are based on a general four-step scheme that has a resemblance to the backward differentiation formulas. We also present an extension to the composite strategy of the Bathe method. Appropriate values for the algorithmic parameters are determined based on considerations of stability and dissipativity, and less dissipative members of each algorithm have been identified. We demonstrate the convergence characteristics of the proposed algorithms with a nonlinear dynamic problem having analytic solutions, and test these algorithms with several three-dimensional nonlinear …

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.

Luminescence Enhancement Of Cdte Nanostructures In Laf3:Ce/Cdte Nanocomposites, Mingzhen Yao, Xing Zhang, Lun Ma, Wei Chen, Alan G. Joly, Jinsong Huang, Qingwu Wang

Department of Mechanical and Materials Engineering: Faculty Publications

Radiation detection demands new scintillators with high quantum efficiency, high energy resolution, and short luminescence lifetimes. Nanocomposites consisting of quantum dots and Ce³⁺ doped nanophosphors may be able to meet these requirements. Here, we report the luminescence enhancement of LaF₃:Ce/CdTe nanocomposites which were synthesized by a wet chemistry method. CdTe quantum dots in LaF₃:Ce/CdTe nanocomposites are converted into nanowires, while in LaF₃ /CdTe nanocomposites no such conversion is observed. As a result, the CdTe luminescence in LaF₃:Ce/CdTe nanocomposites is enhanced about five times, while in LaF₃ /CdTe nanocomposites no enhancement was …

Synthetic Levers Enabling Control Of Phase, Size And Morphology In Transition Metal Phosphide Nanoparticles (Fe, Ni), Elayaraja Muthuswamy

Wayne State University Dissertations

ABSTRACT

SYNTHETIC LEVERS ENABLING CONTROL OF PHASE, SIZE AND MORPHOLOGY IN TRANSITION METAL PHOSPHIDE NANOPARTICLES (FE, NI)

by

ELAYARAJA MUTHUSWAMY

May 2011

Advisor:Dr. Stephanie L. Brock

Major: Chemistry

Degree: Doctor of Philosophy

This dissertation study focuses on (1) development of a synthetic strategy to control phase in nanoscale iron phosphides; (2) extension of the developed phase control strategy to the nanoscale nickel phosphide system with simultaneous control on size and morphology and (3) illustration of the enhanced reactivity of nanoscale oxide systems.

A synthetic strategy to control phase in nanoscale iron phosphides was developed to prepare phase-pure samples of …

Supercritical Carbon Dioxide Processing Of Nano - Clays And Polymer/Clay Nanocomposites, Mihai Manitiu

Wayne State University Dissertations

Effective dispersion of the fillers in a polymer matrix and improvement of polymer-clay interactions are two key challenges in the field of nanocomposites. A novel processing method that utilizes the unique properties of supercritical carbon dioxide (scCO2) to disperse nano-clay and prepare a series of polymer/clay nanocomposites with enhanced properties was explored.

Significant dispersion was achieved using the scCO2 process with Cloisite 10A without the presence of an organic phase as evident by the absence of the diffraction peak in WAXD and the presence of individual tactoids that lost their parallel registry. The expanded flexible structure of the scCO2 processed …

Nanoscale Functionalization And Characterization Of Surfaces With Hydrogel Patterns And Biomolecules, Hariharasudhan Chirra Dinakar

University of Kentucky Doctoral Dissertations

The advent of numerous tools, ease of techniques, and concepts related to nanotechnology, in combination with functionalization via simple chemistry has made gold important for various biomedical applications. In this dissertation, the development and characterization of planar gold surfaces with responsive hydrogel patterns for rapid point of care sensing and the functionalization of gold nanoparticles for drug delivery are highlighted.

Biomedical micro- and nanoscale devices that are spatially functionalized with intelligent hydrogels are typically fabricated using conventional UV-lithography. Herein, precise 3-D hydrogel patterns made up of temperature responsive crosslinked poly(N-isopropylacrylamide) over gold were synthesized. The XY control of the hydrogel …

Quantum Approach To Electronic Noise Calculations In The Presence Of Electron-Phonon Interactions, Hong-Hyun Park, Gerhard Klimeck

Birck and NCN Publications

A quantum-mechanical approach to the calculation of electronic noise for nanoscale devices is presented. This method is based on the nonequilibrium Green’s-function formalism with electron-phonon scattering mechanisms and takes the effects of the Pauli exclusion principle and the long-range Coulomb interactions into account. As examples the drain current noise characteristics of silicon nanowire transistors at room temperature are simulated. The drain current noise in the saturation regime is primarily shot-noise dominant but is suppressed for higher gate biases due to the electron-electron correlation in the channel region. The role of electron-phonon interactions on noise, the transition from thermal to shot …

Accurate Force Spectroscopy In Tapping Mode Atomic Force Microscopy In Liquids, Xin Xu, John Melcher, Arvind Raman

Birck and NCN Publications

Existing force spectroscopy methods in tapping mode atomic force microscopy (AFM) such as higher harmonic inversion [M. Stark, R. W. Stark, W. M. Heckl, and R. Guckenberger, Proc. Natl. Acad. Sci. U. S. A. 99, 8473 (2002)] or scanning probe acceleration microscopy [J. Legleiter, M. Park, B. Cusick, and T. Kowalewski, Proc. Natl. Acad. Sci. U. S. A. 103, 4813 (2006)] or integral relations [M. Lee and W. Jhe, Phys. Rev. Lett. 97, 036104 (2006); S. Hu and A. Raman, Nanotechnology 19, 375704 (2008); H. Holscher, Appl. Phys. Lett. 89, 123109 (2006); A. J. Katan, Nanotechnology 20, 165703 (2009)] require …

Molecular Modulation Of Schottky Barrier Height In Metal-Molecule-Silicon Diodes: Capacitance And Simulation Results, Adina Scott, Chad Risko, Nicholas Valley, Mark A. Ratner, David B. Janes

Birck and NCN Publications

There is considerable current interest in using molecular materials to influence the surface potential of semiconductor devices for nanoelectronic and sensing applications. We present experimental capacitance-voltage results showing that systematic Schottky barrier height modulation can be achieved using dipolar molecular layers in gold-molecule-silicon devices. A computational methodology that combines quantum chemistry and traditional electrostatic calculations is used to explore various physical effects that can influence barrier heights in such systems. Nonidealities such as silicon surface states can influence both the potential profile within the device and the validity of the extracted barrier height. Our devices exhibit low surface state densities, …

On Landauer Versus Boltzmann And Full Band Versus Effective Mass Evaluation Of Thermoelectric Transport Coefficients, Changwook Jeong, Raseong Kim, Mathieu Luisier, Supriyo Datta, Mark S. Lundstrom

Birck and NCN Publications

Using a full band description of electronic bandstructure, the Landauer approach to diffusive transport is mathematically related to the solution of the Boltzmann transport equation, and expressions for the thermoelectric parameters in both formalisms are presented. Quantum mechanical and semiclassical techniques to obtain from a full description of the bandstructure, E(k), the density of modes in the Landauer approach or the transport distribution in the Boltzmann solution are compared and thermoelectric transport coefficients are evaluated. Several example calculations for representative bulk materials are presented and the full band results are related to the more common effective mass formalism. Finally, given …

Theory Of ‘Selectivity’ Of Label-Free Nanobiosensors – A Geometro-Physical Perspective, Pradeep R. Nair, Muhammad A. Alam

Birck and NCN Publications

Modern label-free biosensors are generally far more sensitive and require orders of magnitude less incubation time compared to their classical counterparts. However, a more important characteristic regarding the viability of this technology for applications in Genomics/Proteomics is defined by the ‘Selectivity’, i.e., the ability to concurrently and uniquely detect multiple target biomolecules in the presence of interfering species. Currently, there is no theory of Selectivity that allows optimization of competing factors and there are few experiments to probe this problem systematically. In this article, we use the elementary considerations of surface exclusion, diffusion limited transport, and void distribution function to …

Reactive Molecular Dynamics: Numerical Methods And Algorithmic Techniques, Hasan Metin Aktulga, Shailaja Pandit, Adri C. T. Van Duin, Ananth Y. Grama

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

Modeling atomic and molecular systems requires computation-intensive quantum mechanical methods such as, but not limited to, density functional theory (DFT) [11]. These methods have been successful in predicting various properties of chemical systems at atomistic detail. Due to the inherent nonlocality of quantum mechanics, the scalability of these methods ranges from O(N3) to O(N7) depending on the method used and approximations involved. This significantly limits the size of simulated systems to a few thousands of atoms, even on large scale parallel platforms. On the other hand, classical approximations of quantum systems, although computationally (relatively) easy to implement, yield simpler models …

Weighted Matrix Ordering And Parallel Banded Preconditioners For Iterative Linear System Solvers, Murat Manguoglu, Mehmet Koyuturk, Ahmed Sameh, Ananth Y. Grama

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

The emergence of multicore architectures and highly scalable platforms motivates the development of novel algorithms and techniques that emphasize concurrency and are tolerant of deep memory hierarchies, as opposed to minimizing raw FLOP counts. While direct solvers are reliable, they are often slow and memory-intensive for large problems. Iterative solvers, on the other hand, are more efficient but, in the absence of robust preconditioners, lack reliability. While preconditioners based on incomplete factorizations ( whenever they exist) are effective for many problems, their parallel scalability is generally limited. In this paper, we advocate the use of banded preconditioners instead and introduce …

Real-Time Monitoring Of Contact Behaviour Of Rf Mems Switches With A Very Low Power Cmos Capactive Sensor Interface, Adam Fruehling, Mohammad Abu Khater, Byunghoo Jung, Dimitrios Peroulis

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

This paper presents the first ultra-low power, fully electronic methodology for real-time monitoring of the dynamic behavior of RF MEMS switches. The measurement is based on a capacitive readout circuit composed of 67 transistors with 105 µm x 105 µm footprint consuming as little as 60 µW. This is achieved by accurately sensing the capacitance change around the contact region at sampling rates from 10 kHz to 5 MHz. Experimental and simulation results show that times of not only the first contact event but also all subsequent contact bounces can be accurately measured with this technique without interfering with the …

A Viscoelastic-Aware Experimentally-Derived Model For Analog Rf Mems Varactors, Hao-Han Hsu, Dimitrios Peroulis

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

In this paper we present, for the ¯rst time, an experimentally-extracted model for the spring con- stant and tuning range of an analog RF-MEMS var- actor that includes viscoelastic e®ects in RF-MEMS devices. By utilizing a bi-state bias condition with one state lasting 60 minutes and the other 1 minute, this model focuses on capturing the true electrome- chanical behavior of the varactor. An experimental setup with very high long-term accuracy is created to measure capacitance of the varactor up to 1,370 hours. The impact of these e®ects and the e®ective- ness of the model are demonstrated on a tunable- …

Unusual Scaling Obsrvations In The Quality Factors Of Cantilevered Carbon Nanotube Resonators, Ajit K. Vallabhaneni, Jeffrey F. Rhoads, Xiulin Ruan, Jayathi Y. Murthy

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

This work examines the quality factors (Q factors) of resonance associated with the axial and transverse vibrations of single-wall carbon nanotube (SWCNT) resonators through the use of molecular dynamics (MD) simulation. Specifically, the work investigates the effect of device length, diameter, and chirality, as well as temperature, on the resonant frequency and quality factor of these devices, and benchmarks the results of MD simulation against classical theories of energy dissipation. Of note are the facts that the quality factors associated with transverse vibration decrease with increasing device diameter and are largely insensitive to chirality. Additionally, quality factors increase with increasing …

Far-Field Optical Nanoscopy Based On Continuous Wave Laser Stimulated Emission Depletion, C. Kuang, Wei Zhao, Guiren Wang

Faculty Publications

Stimulated emission depletion (STED) microscopy is one of the breakthrough technologies that belong to far-field optical microscopy and can achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave lasers with different wavelengths, i.e., violet and green lasers for excitation and STED, respectively. Fluorescent dyes Coumarin 102 and Atto 390 are used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a microscope slide, which is coated with the nanoparticles, indicates that a …

Quantum Dot Quantum Computation In Iii-V Type Semiconductor, Sanjay K. Prabhakar

Legacy Theses & Dissertations (2009 - 2024)

Among recent proposals for next-generation, non-charge-based logic is the notion that a single electron can be trapped and spin of the electron can be manipulated through the application of gate potentials. In the thesis, there are two major contributions of the manipulation of electron spin. In regard to the first contribution, we present numerical simulations of such a spin in single electron devices for realistic asymmetric potentials in electrostatically confined quantum dot. Using analytical and numerical techniques we show that breaking in-plane rotational symmetry of the confining potential by applied gate voltage leads to a significant effect on the tuning …

Investigation Of The Threshold Voltage Shift Effect Of La2o3 On Tin/Hfo2/La2o3/Sio2/Si Stacks, Ming Di

Legacy Theses & Dissertations (2009 - 2024)

The semiconductor industry continues to scale (shrink) transistor dimensions to both increase the number of transistors per integrated circuit and their speed. One important aspect of scaling is the need to decrease the equivalent oxide thickness of the transistor gate dielectric while minimizing leakage current. Traditional thin layer SiO2 or SiOxNy films have been replaced by higher dielectric constant film stacks Here we study one example, the HfO2/La2O3/SiO2 stack. This dissertation describes an investigation of the use of La2O3 to reduce the threshold voltage of TiN/HfO2/SiO2/Si stacks (high-k/metal gate stacks). A significant aspect of this study is the determination of …

A Study Of Reticle Non-Flatness Induced Image Placement Error In Extreme Ultraviolet Lithography, Sudharshanan Raghunathan

Legacy Theses & Dissertations (2009 - 2024)

As the semiconductor industry continues scaling devices to smaller sizes, the need for next generation lithography technology for fabricating these small structures has always been at the forefront. Over the past few years, conventional optical lithography technology which has adopted a series of resolution enhancement techniques to support the scaling needs is expected to run out of steam in the near future. Extreme Ultra Violet lithography (EUVL) is being actively pursued by the semiconductor industry as one of the most promising next generation lithographic technologies. Most of the issues unique to EUVL arise from the use of 13.5 nm light …

Fabrication And Characterization Of Nanomaterials Grown By Electron Beam Induced Deposition Process, Juntao Li

Legacy Theses & Dissertations (2009 - 2024)

Platinum&ndash and tungsten&ndashcontaining materials were grown on bulk substrates from a variety of precursors including (CH₃)₃CH₃C₅H₄Pt, W(CO)₆, WF₆, and Pt(PF₃)₄ in either a high vacuum dual beam focused ion beam/scanning electron microscope (FIB&ndashSEM) or an environmental scanning electron microscope (ESEM). The effects of deposition conditions on the growth kinetics, microstructure and composition of the grown materials, structural and chemical homogeneity of impurities inside the deposits as well as the resistivity were investigated.

Nanoabrasives Retention And Removal Mechanisms In Polyurethane Pads For Copper Cmp, Iftikhar Ul-Hasan

Legacy Theses & Dissertations (2009 - 2024)

The continued reduction in integrated circuit (IC) feature size requires similar reductions in surface defectivity. A key source of surface defects in IC fabrication processes stems from nanoabrasives used in chemical-mechanical planarization (CMP) processing. During CMP processing, polished surfaces are more vulnerable to defects including scratching, nanoabrasive particle adhesion and nanoabrasive agglomerate adhesion. The removal of these nano-sized particles is a priority for the IC fabrication industry and is reflected in the 2008 ITRS defect budget. However, there is insufficient technical understanding regarding the retention of residual nanoabrasives on the surfaces of the CMP pad following a CMP process and …