Physical Sciences and Mathematics Commons^™

Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory

Faculty Publications

Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain …

Some Contemporary Issues In Software Reliability., Vignesh Subrahmaniam Dr.

Doctoral Theses

No abstract provided.

Spintronic Circuits: The Building Blocks Of Spin-Based Computation, Roshan Warman

Undergraduate Journal of Mathematical Modeling: One + Two

In the most general situation, binary computation is implemented by means of microscopic logical gates known as transistors. According to Moore’s Law, the size of transistors will half every two years, and as these transistors reach their fundamental size limit, the quantum effects of the electrons passing through the transistors will be observed. Due to the inherent randomness of these quantum fluctuations, the basic binary logic will become uncontrollable. This project describes the basic principle governing quantum spin-based computing devices, which may provide an alternative to the conventional solid-state computing devices and circumvent the technological limitations of the current implementation …

Solution-Printed Organic Semiconductor Blends Exhibiting Transport Properties On Par With Single Crystals, Muhammad R. Niazi, Ruipeng Li, Er Qiang Li, Ahmad R. Kirmani, Maged Abdelsamie, Qingxiao Wang, Wenyang Pan, Marcia M. Payne, John E. Anthony, Detlef-M. Smilgies, Sigurdur T. Thoroddsen, Emmanuel P. Giannelis, Aram Amassian

Chemistry Faculty Publications

Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm²V⁻¹s⁻¹, low threshold …

Enhancing The Performance Of Organic Thin Film Transistors By Cross-Linking The Organic Gate Dielectric, Soheila Naderi Gohar

Electronic Thesis and Dissertation Repository

Amongst various surface modification techniques, hyperthermal hydrogen induced cross-linking (HHIC) has been used to modify the surface of polymeric samples. In this novel and innovative technique neutral hydrogen projectiles with appropriate kinetic energy are produced to generate carbon radicals on the impacted surface through the collision-induced C-H bond breaking. Subsequently, this phenomenon results in cross-linking hydrocarbon chains in the treated polymeric samples.

Verifying the validity of cross-linking process through experiments is the target of first part of presented dissertation. Spin-coated poly(methyl methacrylate) (PMMA) films on silicon wafer were exposed to hydrogen projectiles for different durations, while the other conditions related …

Variational Multiscale Models For Charge Transport, Guo-Wei Wei, Qiong Zheng, Zhan Chen, Kelin Xia

Zhan Chen

This work presents a few variational multiscale models for charge transport in complex physical, chemical, and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors, and ion channels. An essential ingredient of the present models, introduced in an earlier paper [Bull. Math. Biol., 72 (2010), pp. 1562--1622], is the use of the differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, while dynamically coupling discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to …

On Co-Optimization Of Constrained Satisfiability Problems For Hardware Software Applications, Kunal Ganeshpure

Doctoral Dissertations 1896 - February 2014

Manufacturing technology has permitted an exponential growth in transistor count and density. However, making efficient use of the available transistors in the design has become exceedingly difficult. Standard design flow involves synthesis, verification, placement and routing followed by final tape out of the design. Due to the presence of various undesirable effects like capacitive crosstalk, supply noise, high temperatures, etc., verification/validation of the design has become a challenging problem. Therefore, having a good design convergence may not be possible within the target time, due to a need for a large number of design iterations.

Capacitive crosstalk is one of the …

Single-Electron Transport Spectroscopy Studies Of Magnetic Molecules And Nanoparticles, Firoze Haque

Electronic Theses and Dissertations

Magnetic nanoparticles and molecules, in particular ferromagnetic noble metal nanoparticles, molecular magnet and single-molecule magnets (SMM), are perfect examples to investigate the role of quantum mechanics at the nanoscale. For example, SMMs are known to reverse their magnetization by quantum tunneling in the absence of thermal excitation and show a number of fundamental quantum mechanical manifestations, such as quantum interference effects. On the other hand, noble metal nanoparticles are found to behave ferromagnetically for diameters below a few nanometers. Some of these manifestations are still intriguing, and novel research approaches are necessary to advance towards a more complete understanding of …

The Combined Effects Of Radio Frequency And Gamma Irradiation On P-Channel Mosfets, Joshua D. Daniel

Theses and Dissertations

The purpose of this research was to investigate the combined effects of continuous gigahertz radio frequency signals and gamma irradiation on the threshold voltage of metal oxide semiconductor field effect transistors. The combined effects of gigahertz radio frequency waves and gamma irradiation on electronics presents a new challenge in electronic warfare and little is known of the combined effect on threshold voltage damage and recovery. The Fairchild NDS352AP, a commonly used commercial device, was irradiated by a cobalt-60 source under a +5 V bias with and without a radio frequency signal applied to the gate. The threshold voltage was measured …

Inelastic Electron Tunneling Via Molecular Vibrations In Single-Molecule Transistors, L H. Yu, Z K. Keane, Jacob W. Ciszek, L Cheng, M P. Stewart, J M. Tour, D Natelson

Chemistry: Faculty Publications and Other Works

In single-molecule transistors, we observe inelastic cotunneling features that correspond energetically to vibrational excitations of the molecule, as determined by Raman and infrared spectroscopy. This is a form of inelastic electron tunneling spectroscopy of single molecules, with the transistor geometry allowing in situ tuning of the electronic states via a gate electrode. The vibrational features shift and change shape as the electronic levels are tuned near resonance, indicating significant modification of the vibrational states. When the molecule contains an unpaired electron, we also observe vibrational satellite features around the Kondo resonance.

Vertical Nanowire Transistors With Low Leakage Current, Jie Chen, M. C. Lux-Steiner, Rolf Kӧnenkamp, S. Klaumünzer

Physics Faculty Publications and Presentations

A vertical field-effect transistor based on semiconductor nanowires is reported. The fabrication of the device uses a self-supporting flexible nanostructured polymer foil as a template and an electrochemical growth technique for the preparation of the semiconductor. The fabrication process is substantially simpler, and the mechanical robustness is strongly increased as compared to the original device. The channel region of the transistor has a diameter of ∼100 nm and a length of ∼50 nm. Operation in the hole depletion mode allows a change of the transfer conductance by ∼50% when the gate voltages is changed in the range ∓1 V. The …

Vertical Nanowire Transistor In Flexible Polymer Foil, Jie Chen, Rolf Könenkamp

Physics Faculty Publications and Presentations

Fabrication and operation of a vertical nanowire field-effect transistor is reported. The device is prepared by growing vertical wires in the cylindrical pores of a polymer foil stack. The nanowirediameter is approximately 100 nm, the packing density up to 10⁸ cm⁻². The polymer foil stack consists of two polymer layers and an intermediate metal layer. Cylindrical holes are prepared in this stack by using fast ion irradiation and subsequent etching. Well-defined cylindrical openings with diameters between 50 and 150 nm are obtained. The semiconductor growth involves electrodeposition of the p-type quaternary compound CuSCN. Electrical measurements on first devices show transistor …

Eigen Modes And Ferromagnetic Resonance Line Width Of Inhomogeneous Thin Films, R. D. Mcmichael, Andrew Kunz, D. J. Twisselmann

Physics Faculty Research and Publications

In this paper, we describe modeling of the effects of magnetic inhomogeneity on ferromagnetic resonance line width using eigen mode analyses of inhomogeneous thin magnetic films.

Normal Mode Mixing And Ferromagnetic Resonance Linewidth, Andrew Kunz, R. D. Mcmichael

Physics Faculty Research and Publications

The normal modes of an inhomogeneous thin film are obtained by diagonalization of the perturbed Hamiltonian. The resulting modes are mixtures of the spin-wave modes and the uniform mode. We find that the ferromagnetic resonance intensity spectrum of the diagonalized system has a Lorentzian profile, and that the results correspond to the two-magnon model for weak perturbations. For stronger perturbations, the density of states is smoothed, and the spectrum becomes asymmetric due to the low-frequency cutoff of the spin-wave manifold. The technique is expected to be valid for perturbation amplitudes that are large enough to invalidate the assumptions of the …

Routing Algorithms For Channels, Switchboxes And Mcm's In Vlsi Layout Design., Sandip Das Dr.

Doctoral Theses

The term Very Large Scale Integration (VLSI) reflects the capability of semi- conductor industry to fabricate a complex electronic circuit consisting of millions of components on a single silicon substrate. The growth of semiconductor technol- ogy in recent years has been described by "Moore's law", enunciated in the late 1960s, which projected quadrupling of components in a chip in every three to four years. Several factors contributed to this tremendous growth : (i) reduction of line width of the basic device and interconnection wires due to the development of high- resolution lithographic techniques and improved processing capabilities, (ii) increase in …

Supralinear Photoconductivity Of Copper Doped Semi-Insulating Gallium Arsenide, K. H. Schoenbach, R. P. Joshi, F. Peterkin, R. L. Druce

Bioelectrics Publications

We report on the intensity dependent supralinear photoconductivity in GaAs:Si:Cu material. The results of our measurements show that the effective carrier lifetime can change over two orders of magnitude with variations in the intensity of the optical excitation. A threshold intensity level has been observed and can be related to the occupancy of the deep copper level. Numerical simulations have also been carried out to analyze the trapping dynamics. The intensity dependent lifetimes obtained from the simulations match the experimental data very well. Finally, based on the nonlinear intensity dependence of the effective lifetimes, a possible low‐energy phototransistor application for …