Open Access. Powered by Scholars. Published by Universities.®

Nanoscience and Nanotechnology Commons™

Open Access. Powered by Scholars. Published by Universities.®

2013

Series

Discipline
Institution
Keyword
Publication

Articles 31 - 60 of 102

Full-Text Articles in Nanoscience and Nanotechnology

Quantum Coherence And Entanglement In The Avian Compass, James A. Pauls, Yiteng Zhang, Gennady P. Berman, Sabre Kais Jun 2013

Quantum Coherence And Entanglement In The Avian Compass, James A. Pauls, Yiteng Zhang, Gennady P. Berman, Sabre Kais

Birck and NCN Publications

The radical-pair mechanism is one of two distinct mechanisms used to explain the navigation of birds in geomagnetic fields, however little research has been done to explore the role of quantum entanglement in this mechanism. In this paper we study the lifetime of radical-pair entanglement corresponding to the magnitude and direction of magnetic fields to show that the entanglement lasts long enough in birds to be used for navigation. We also find that the birds appear to not be able to orient themselves directly based on radical-pair entanglement due to a lack of orientation sensitivity of the entanglement in the …

Go to article

Existence Of Negative Differential Thermal Conductance In One-Dimensional Diffusive Thermal Transport, Jiuning Hu, Yong P. Chen Jun 2013

Existence Of Negative Differential Thermal Conductance In One-Dimensional Diffusive Thermal Transport, Jiuning Hu, Yong P. Chen

Birck and NCN Publications

We show that in a finite one-dimensional (1D) system with diffusive thermal transport described by the Fourier's law, negative differential thermal conductance (NDTC) cannot occur when the temperature at one end is fixed and there are no abrupt junctions. We demonstrate that NDTC in this case requires the presence of junction(s) with temperature-dependent thermal contact resistance (TCR). We derive a necessary and sufficient condition for the existence of NDTC in terms of the properties of the TCR for systems with a single junction. We show that under certain circumstances we even could have infinite (negative or positive) differential thermal conductance …

Go to article

Spin-Valley Lifetimes In A Silicon Quantum Dot With Tunable Valley Splitting, C. H. Yang, A. Rossi, R. Ruskov, N. S. Lai, F. A. Mohiyaddin, S. Lee, C. Tahan, Gerhard Klimeck, A. Morello, A. S. Dzurak Jun 2013

Spin-Valley Lifetimes In A Silicon Quantum Dot With Tunable Valley Splitting, C. H. Yang, A. Rossi, R. Ruskov, N. S. Lai, F. A. Mohiyaddin, S. Lee, C. Tahan, Gerhard Klimeck, A. Morello, A. S. Dzurak

Birck and NCN Publications

Although silicon is a promising material for quantum computation, the degeneracy of the conduction band minima (valleys) must be lifted with a splitting sufficient to ensure the formation of well-defined and long-lived spin qubits. Here we demonstrate that valley separation can be accurately tuned via electrostatic gate control in a metal-oxide-semiconductor quantum dot, providing splittings spanning 0.3-0.8 meV. The splitting varies linearly with applied electric field, with a ratio in agreement with atomistic tight-binding predictions. We demonstrate single-shot spin read-out and measure the spin relaxation for different valley configurations and dot occupancies, finding one-electron lifetimes exceeding 2 s. Spin relaxation …

Go to article

Atmospheric Pressure He-Air Plasma Jet: Breakdown Process And Propagation Phenomenon, Asma Begum, Mounir Laroussi, Mohammad Rasel Pervez Jun 2013

Atmospheric Pressure He-Air Plasma Jet: Breakdown Process And Propagation Phenomenon, Asma Begum, Mounir Laroussi, Mohammad Rasel Pervez

Electrical & Computer Engineering Faculty Publications

In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet …

Go to article

Thickness-Shear And Thickness-Twist Vibrations Of Circular At-Cut Quartz Resonators, Huijing He, Jiashi Yang, Qing Jiang Jun 2013

Thickness-Shear And Thickness-Twist Vibrations Of Circular At-Cut Quartz Resonators, Huijing He, Jiashi Yang, Qing Jiang

Department of Mechanical and Materials Engineering: Faculty Publications

Exact solutions for free vibration frequencies and modes are obtained for thickness-shear and thickness-twist vibrations of unelectroded circular AT-cut quartz plates governed by the two-dimensional scalar differential equation derived by Tiersten and Smythe. Comparisons are made with experimental results and the widely-used perturbation solution by Tiersten and Smythe under the assumption of weak in-plane anisotropy. Our solution is found to be much closer to the experimental results than the perturbation solution . For the frequency of the fundamental thickness- shear mode, the error of the perturbation method is 0.4549%, significant in resonator applications.

Go to article

Cross-Plane Thermoelectric Transport In P-Type La0.67sr0.33mno3/Lamno3 Oxide Metal/Semiconductor Superlattices, Pankaj Jha, Timothy D. Sands, Philip Jackson, Cory Bomberger, Tela Favaloro, Stephen Hodson, Joshua Zide, Xianfan Xu, Ali Shakouri May 2013

Cross-Plane Thermoelectric Transport In P-Type La0.67sr0.33mno3/Lamno3 Oxide Metal/Semiconductor Superlattices, Pankaj Jha, Timothy D. Sands, Philip Jackson, Cory Bomberger, Tela Favaloro, Stephen Hodson, Joshua Zide, Xianfan Xu, Ali Shakouri

Birck and NCN Publications

The cross-plane thermoelectric transport properties of La0.67Sr0.33MnO3 (LSMO)/LaMnO3 (LMO) oxide metal/semiconductor superlattices were investigated. The LSMO and LMO thin-film depositions were performed using pulsed laser deposition to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate substrates. X-ray diffraction and high-resolution reciprocal space mapping indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively, this coupled-plasma reactive-ion etching. The crossplane electrical conductivity data for LSMO/LMO superlattices reveal a lowering of the effective barrier height to 223 meV as well as an increase in cross-plane conductivity by …

Go to article

Photonically Excited Electron Emission From Modified Graphitic Nanopetal Arrays, Patrick T. Mccarthy, Scott J. Vander Laan, David B. Janes, Timothy S. Fisher May 2013

Photonically Excited Electron Emission From Modified Graphitic Nanopetal Arrays, Patrick T. Mccarthy, Scott J. Vander Laan, David B. Janes, Timothy S. Fisher

Birck and NCN Publications

Efficient electron emission for energy conversion requires a low work function and a stable emitter material. The work function of graphene-based carbon materials can decrease significantly by intercalation with alkali metals, thus increasing their emission current. In this work, electron emission from potassium-intercalated carbon nanosheet extensions grown on electrode graphite is investigated. These petal-like structures, composed of 5-25 layers of graphene, are synthesized using microwave plasma chemical vapor deposition. Samples are intercalated with potassium, and a hemispherical energy analyzer is used to measure the emission intensity caused by both thermal and photonic excitation. The emission from the potassium-intercalated structures is …

Go to article

Direct Pulsed Laser Crystallization Of Nanocrystals For Absorbent Layers In Photovoltaics: Multiphysics Simulation And Experiment, Martin Y. Zhang, Qiong Nian, Yung Shin, Gary J. Cheng May 2013

Direct Pulsed Laser Crystallization Of Nanocrystals For Absorbent Layers In Photovoltaics: Multiphysics Simulation And Experiment, Martin Y. Zhang, Qiong Nian, Yung Shin, Gary J. Cheng

Birck and NCN Publications

Direct pulsed laser crystallization (DPLC) of nanoparticles of photoactive material-Copper Indium Selenide (nanoCIS) is investigated by multiphysics simulation and experiments. Laser interaction with nanoparticles is fundamentally different from their bulk counterparts. A multiphysics electromagnetic-heat transfer model is built to simulate DPLC of nanoparticles. It is found smaller photoactive nanomaterials (e.g., nanoCIS) require less laser fluence to accomplish the DPLC due to their stronger interactions with incident laser and lower melting point. The simulated optimal laser fluence is validated by experiments observation of ideal microstructure. Selectivity of DPLC process is also confirmed by multiphysics simulation and experiments. The combination effects of …

Go to article

Electrochemical Immunosensing Of Cortisol In An Automated Microfluidic System Towards Point-Of-Care Applications, Abhay Vasudev May 2013

Electrochemical Immunosensing Of Cortisol In An Automated Microfluidic System Towards Point-Of-Care Applications, Abhay Vasudev

FIU Electronic Theses and Dissertations

This dissertation describes the development of a label-free, electrochemical immunosensing platform integrated into a low-cost microfluidic system for the sensitive, selective and accurate detection of cortisol, a steroid hormone co-related with many physiological disorders. Abnormal levels of cortisol is indicative of conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiencies and more recently post-traumatic stress disorder (PTSD). Electrochemical detection of immuno-complex formation is utilized for the sensitive detection of Cortisol using Anti-Cortisol antibodies immobilized on sensing electrodes. Electrochemical detection techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been utilized for the characterization and sensing of the …

Go to article

Structural Modification Of Graphene Sheets To Create A Dense Network Of Defect Sites, Mei-Xian Wang, Qi Liu, Zhe-Fei Li, Hong-Fang Sun, Eric A. Stach, Jian Xie May 2013

Structural Modification Of Graphene Sheets To Create A Dense Network Of Defect Sites, Mei-Xian Wang, Qi Liu, Zhe-Fei Li, Hong-Fang Sun, Eric A. Stach, Jian Xie

Birck and NCN Publications

Pt/graphene composites were synthesized by loading platinum nanoparticles onto graphene and etched at 1000 degrees C in a hydrogen atmosphere. This results in the formation of a dense array of nanostructured defect sites in the graphene, including trenches, nanoribbons, islands, and holes. These defect sites result in an increase in the number of unsaturated carbon atoms and, consequently, enhance the interaction of the CO2 molecules with the etched graphene. This leads to a high capacity for storing CO2; 1 g of the etched samples can store up to 76.3 cm(3) of CO2 at 273 K under ambient pressure.

Go to article

Nanowire Metal-Insulator-Metal Plasmonic Devices, Joseph W. Haus, Li Li, Cong Deng, Nkorni Katte, Michael Scalora, Domenico De Ceglia, Maria Antonietta Vincenti May 2013

Nanowire Metal-Insulator-Metal Plasmonic Devices, Joseph W. Haus, Li Li, Cong Deng, Nkorni Katte, Michael Scalora, Domenico De Ceglia, Maria Antonietta Vincenti

Electro-Optics and Photonics Faculty Publications

In this paper we theoretically study the responsivity of Metal-Insulator-Metal nanostructures to light illumination over a broad wavelength band (1 - 25 microns) and we examine the role of a local field enhancement and electrostatic field on the responsivity.

Go to article

Quantum Criticality Analysis By Finite-Size Scaling And Exponential Basis Sets, Fahhad H. Alberbi, Sabre Kais Apr 2013

Quantum Criticality Analysis By Finite-Size Scaling And Exponential Basis Sets, Fahhad H. Alberbi, Sabre Kais

Birck and NCN Publications

We combine the finite-size scaling method with the mesh-free spectral method to calculate quantum critical parameters for a given Hamiltonian. The basic idea is to expand the exact wave function in a finite exponential basis set and extrapolate the information about system criticality from a finite basis to the infinite basis set limit. The used exponential basis set, though chosen intuitively, allows handling a very wide range of exponential decay rates and calculating multiple eigenvalues simultaneously. As a benchmark system to illustrate the combined approach, we choose the Hulthen potential. The results show that the method is very accurate and …

Go to article

Broadband Enhancement Of Spontaneous Emission From Nitrogen-Vacancy Centers In Nanodiamonds By Hyperbolic Metamaterials, Mikhail Y. Shalaginov, Satoshi Ishii, J. Liu, Joseph Irudayaraj, A. Lagutchev, Alexander V. Kildishev, Vladimir M. Shalaev Apr 2013

Broadband Enhancement Of Spontaneous Emission From Nitrogen-Vacancy Centers In Nanodiamonds By Hyperbolic Metamaterials, Mikhail Y. Shalaginov, Satoshi Ishii, J. Liu, Joseph Irudayaraj, A. Lagutchev, Alexander V. Kildishev, Vladimir M. Shalaev

Birck and NCN Publications

We experimentally demonstrate a broadband enhancement of emission from nitrogen-vacancy centers in nanodiamonds. The enhancement is achieved by using a multilayer metamaterial with hyperbolic dispersion. The metamaterial is fabricated as a stack of alternating gold and alumina layers. Our approach paves the way towards the construction of efficient single-photon sources as planar on-chip devices. (C) 2013 AIP Publishing LLC.

Go to article

Pre-Breakdown Evaluation Of Gas Discharge Mechanisms In Microgaps, Abbas Semnani, Ayyaswamy Venkattraman, Alina A. Alexeenko, Dimitrios Peroulis Apr 2013

Pre-Breakdown Evaluation Of Gas Discharge Mechanisms In Microgaps, Abbas Semnani, Ayyaswamy Venkattraman, Alina A. Alexeenko, Dimitrios Peroulis

Birck and NCN Publications

The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown. (C) 2013 AIP Publishing LLC

Go to article

Evidence For Effective Mass Reduction In Gaas/Algaas Quantum Wells, A. T. Hatke, M. A. Zudov, J. D. Watson, Michael J. Manfra, L. N. Pfeiffer, K. W. West Apr 2013

Evidence For Effective Mass Reduction In Gaas/Algaas Quantum Wells, A. T. Hatke, M. A. Zudov, J. D. Watson, Michael J. Manfra, L. N. Pfeiffer, K. W. West

Birck and NCN Publications

We have performed microwave photoresistance measurements in high mobility GaAs/AlGaAs quantum wells and investigated the value of the effective mass. Surprisingly, the effective mass, obtained from the period of microwave-induced resistance oscillations, is found to be about 12% lower than the band mass in GaAs, m(b)*. This finding provides strong evidence for electron-electron interactions which can be probed by microwave photoresistance in very high Landau levels. In contrast, the measured magnetoplasmon dispersion revealed an effective mass which is close to m(b)*, in accord with previous studies. DOI: 10.1103/PhysRevB.87.161307

Go to article

Thermoelectric Properties Of Epitaxial Scn Films Deposited By Reactive Magnetron Sputtering Onto Mgo(001) Substrates, Polina V. Burmistrova, Jesse Maassen, Tela Favaloro, Bivas Saha, Shuaib Salamat, Yee Rui Koh, Mark S. Lundstrom, Ali Shakouri, Timothy D. Sands Apr 2013

Thermoelectric Properties Of Epitaxial Scn Films Deposited By Reactive Magnetron Sputtering Onto Mgo(001) Substrates, Polina V. Burmistrova, Jesse Maassen, Tela Favaloro, Bivas Saha, Shuaib Salamat, Yee Rui Koh, Mark S. Lundstrom, Ali Shakouri, Timothy D. Sands

Birck and NCN Publications

Epitaxial ScN(001) thin films were grown on MgO(001) substrates by dc reactive magnetron sputtering. The deposition was performed in an Ar/N-2 atmosphere at 2 x 10(-3) Torr at a substrate temperature of 850 degrees C in a high vacuum chamber with a base pressure of 10(-8) Torr. In spite of oxygen contamination of 1.6 +/- 1 at. %, the electrical resistivity, electron mobility, and carrier concentration obtained from a typical film grown under these conditions by room temperature Hall measurements are 0.22 m Omega cm, 106 cm(2) V-1 s(-1), and 2.5 x 10(20) cm(-3), respectively. These films exhibit remarkable thermoelectric …

Go to article

Length And Temperature Dependent 1/F Noise In Vertical Single-Walled Carbon Nanotube Arrays, Robert A. Sayer, Jeffrey D. Engerer, N. S. Vidhyadhiraja, Timothy S. Fisher Apr 2013

Length And Temperature Dependent 1/F Noise In Vertical Single-Walled Carbon Nanotube Arrays, Robert A. Sayer, Jeffrey D. Engerer, N. S. Vidhyadhiraja, Timothy S. Fisher

Birck and NCN Publications

We report measurements of temperature-and length-dependent 1/f noise in vertical single-walled carbon nanotube (SWCNT) arrays. Carbon nanotubes are synthesized in a porous anodic alumina template with sub-micrometer channel lengths ranging from 100 to 700 nm. A significant difference is observed in the 1/f noise magnitude of quasi-ballistic and diffusive SWCNT devices, with quasi-ballistic devices exhibiting 1/f noise levels that are one to two orders of magnitude less than diffusively conducting devices. Furthermore, 1/f noise was measured from 90 to 400 K, and the noise prefactor decreased significantly at temperatures below 250 K. (C) 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4800856]

Go to article

Atomic Force Microscopy-Coupled Microcoils For Cellular-Scale Nuclear Magnetic Resonance Spectroscopy, Charilaos Mousoulis, Teimour Maleki, Babak Ziaie, Corey Neu Apr 2013

Atomic Force Microscopy-Coupled Microcoils For Cellular-Scale Nuclear Magnetic Resonance Spectroscopy, Charilaos Mousoulis, Teimour Maleki, Babak Ziaie, Corey Neu

Birck and NCN Publications

We present the coupling of atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) technologies to enable topographical, mechanical, and chemical profiling of biological samples. Here, we fabricate and perform proof-of-concept testing of radiofrequency planar microcoils on commercial AFM cantilevers. The sensitive region of the coil was estimated to cover an approximate volume of 19.4 x 10(3) mu m(3) (19.4 pl). Functionality of the spectroscopic module of the prototype device is illustrated through the detection of H-1 resonance in deionized water. The acquired spectra depict combined NMR capability with AFM that may ultimately enable biophysical and biochemical studies at the …

Go to article

Mechanism Of Fatigue Performance Enhancement In A Laser Sintered Superhard Nanoparticles Reinforced Nanocomposite Followed By Laser Shock Peening, Dong Lin, Chang Ye, Yiliang Liao, Sergey Suslov, Richard Liu, Gary J. Cheng Apr 2013

Mechanism Of Fatigue Performance Enhancement In A Laser Sintered Superhard Nanoparticles Reinforced Nanocomposite Followed By Laser Shock Peening, Dong Lin, Chang Ye, Yiliang Liao, Sergey Suslov, Richard Liu, Gary J. Cheng

Birck and NCN Publications

This study investigates the fundamental mechanism of fatigue performance enhancement during a novel hybrid manufacturing process, which combines laser sintering of superhard nanoparticles integrated nanocomposites and laser shock peening (LSP). Through laser sintering, TiN nanoparticles are integrated uniformly into iron matrix to form a nanocomposite layer near the surface of AISI4140 steel. LSP is then performed on the nanocomposite layer to generate interaction between nanoparticles and shock waves. The fundamental mechanism of fatigue performance enhancement is discussed in this paper. During laser shock interaction with the nanocomposites, the existence of nanoparticles increases the dislocation density and also helps to pin …

Go to article

High-Resolution Correlation Spectroscopy Of 13c Spins Near A Nitrogen-Vacancy Centre In Diamond, Abdelghani Laraoui, Florian Dolde, Christian Burk, Friedemann Reinhard, Jorg Wrachtrup, Carlos A. Meriles Apr 2013

High-Resolution Correlation Spectroscopy Of 13c Spins Near A Nitrogen-Vacancy Centre In Diamond, Abdelghani Laraoui, Florian Dolde, Christian Burk, Friedemann Reinhard, Jorg Wrachtrup, Carlos A. Meriles

Department of Mechanical and Materials Engineering: Faculty Publications

Spin complexes comprising the nitrogen-vacancy centre and neighbouring spins are being considered as a building block for a new generation of spintronic and quantum information processing devices. As assembling identical spin clusters is difficult, new strategies are being developed to determine individual node structures with the highest precision. Here we use a pulse protocol to monitor the time evolution of the 13C ensemble in the vicinity of a nitrogenvacancy centre. We observe long-lived time correlations in the nuclear spin dynamics, limited by nitrogen-vacancy spin–lattice relaxation. We use the host 14N spin as a quantum register and demonstrate that hyperfine-shifted resonances …

Go to article

Thickness-Shear Vibration Of A Rectangular Quartz Plate With Partial Electrodes, Huijing He, Jiashi Yang, John A. Kosinski, Ji Wang Apr 2013

Thickness-Shear Vibration Of A Rectangular Quartz Plate With Partial Electrodes, Huijing He, Jiashi Yang, John A. Kosinski, Ji Wang

Department of Mechanical and Materials Engineering: Faculty Publications

We study free vibration of a thickness-shear mode crystal resonator of AT-cut quartz. The resonator is a rectangular plate partially and symmetrically electroded at the center with rectangular electrodes. A single-mode, three-dimensional equation governing the thickness-shear displacement is used. A Fourier series solution is obtained. Numerical results calculated from the series show that there exist trapped thickness-shear modes whose vibration is mainly under the electrodes and decays rapidly outside the electrodes. The effects of the electrode size and thickness on the trapped modes are examined.

Go to article

Nanopatterning Of Metal-Coated Silicon Surfaces Via Ion Beam Irradiation: Real Time X-Ray Studies Reveal The Effect Of Silicide Bonding, Osman El-Atwani, Sean Gonderman, Alexander Demasi, Anastassiya Suslova, Justin Fowler, Mohamad El-Atwani, Karl Ludwig, Jean Paul Allain Mar 2013

Nanopatterning Of Metal-Coated Silicon Surfaces Via Ion Beam Irradiation: Real Time X-Ray Studies Reveal The Effect Of Silicide Bonding, Osman El-Atwani, Sean Gonderman, Alexander Demasi, Anastassiya Suslova, Justin Fowler, Mohamad El-Atwani, Karl Ludwig, Jean Paul Allain

Birck and NCN Publications

We investigated the effect of silicide formation on ion-induced nanopatterning of silicon with various ultrathin metal coatings. Silicon substrates coated with 10 nm Ni, Fe, and Cu were irradiated with 200 eV argon ions at normal incidence. Real time grazing incidence small angle x-ray scattering (GISAXS) and x-ray fluorescence (XRF) were performed during the irradiation process and real time measurements revealed threshold conditions for nanopatterning of silicon at normal incidence irradiation. Three main stages of the nanopatterning process were identified. The real time GISAXS intensity of the correlated peaks in conjunction with XRF revealed that the nanostructures remain for a …

Go to article

Multifunctional Nanoparticles In Cancer: In Vitro Characterization, In Vivo Distribution, Tingjun Lei Mar 2013

Multifunctional Nanoparticles In Cancer: In Vitro Characterization, In Vivo Distribution, Tingjun Lei

FIU Electronic Theses and Dissertations

A novel biocompatible and biodegradable polymer, termed poly(Glycerol malate co-dodecanedioate) (PGMD), was prepared by thermal condensation method and used for fabrication of nanoparticles (NPs). PGMD NPs were prepared using the single oil emulsion technique and loaded with an imaging/hyperthermia agent (IR820) and a chemotherapeutic agent (doxorubicin, DOX). The size of the void PGMD NPs, IR820-PGMD NPs and DOX-IR820-PGMD NPs were approximately 90 nm, 110 nm, and 125 nm respectively. An acidic environment (pH=5.0) induced higher DOX and IR820 release compared to pH=7.4. DOX release was also enhanced by exposure to laser, which increased the temperature to 42°C. Cytotoxicity of DOX-IR820-PGMD …

Go to article

Full Band Calculations Of The Intrinsic Lower Limit Of Contact Resistivity, Jesse Maassen, C. Jeong, A. Baraskar, M. Rodwell, Mark S. Lundstrom Mar 2013

Full Band Calculations Of The Intrinsic Lower Limit Of Contact Resistivity, Jesse Maassen, C. Jeong, A. Baraskar, M. Rodwell, Mark S. Lundstrom

Birck and NCN Publications

The intrinsic lower limit of contact resistivity (rho(LL)(c)) for InAs, In0.53Ga0.47As, GaSb, and Si is calculated using a full band ballistic quantum transport approach. Surprisingly, our results show that rho(LL)(c) is almost independent of the semiconductor. An analytical model, derived for 1D, 2D, and 3D, correctly reproduces the numerical results and explains why rho(LL)(c) is very similar in all cases. Our analysis sets a minimal carrier density required to meet the International Technology Roadmap for Semiconductors call for rho(c) x 10(-9) Omega-cm(2) by 2023. Comparison with experiments shows there is room for improvement, which will come from optimizing interfacial properties. …

Go to article

Coupled Vibrational Modes In Multiple-Filled Skutterudites And The Effects On Lattice Thermal Conductivity Reduction, Liang Guo, Xianfan Xu, J. R. Salvador, G. P. Meisner Mar 2013

Coupled Vibrational Modes In Multiple-Filled Skutterudites And The Effects On Lattice Thermal Conductivity Reduction, Liang Guo, Xianfan Xu, J. R. Salvador, G. P. Meisner

Birck and NCN Publications

The influence of guest atoms on thermal conduction in filled skutterudites was studied using ultrafast reflectance spectroscopy. Different filling species cause coupled vibrational modes between the guest atoms and the host lattice at different frequencies, which scatter phonons in different spectral spans. Using a Debye model for the measured lattice thermal conductivity together with the measured vibration frequencies and scattering rates, it is shown that scattering due to the coupled vibrational modes has a considerable contribution to the suppression of lattice thermal conduction. This demonstrates that filling with multiple species can efficiently reduce the lattice thermal conductivity in skutterudites. (C) …

Go to article

Shape Memory Metamaterials With Tunable Thermo-Mechanical Response Via Hetero-Epitaxial Integration: A Molecular Dynamics Study, Karthik Guda Vishnu, Alejandro Strachan Mar 2013

Shape Memory Metamaterials With Tunable Thermo-Mechanical Response Via Hetero-Epitaxial Integration: A Molecular Dynamics Study, Karthik Guda Vishnu, Alejandro Strachan

Birck and NCN Publications

We show that nanoscale epitaxial superlattices (SLs) can be used to engineer the energy landscape that governs the martensitic transformation in shape memory alloys and tune their thermo-mechanical response. We demonstrate the approach using large-scale molecular dynamics simulations of a SL material consisting of alternate layers of a shape memory Ni-rich NiAl alloy and NiAl B2 alloy. The non-martensitic NiAl alloy was chosen to reduce the energy barrier that separates the martensite and austenite phases of the SL and its incorporation leads to a reduction in the thermal hysteresis of the transition. This is a desirable feature in applications involving …

Go to article

Thermoreflectance Imaging Of Sub 100 Ns Pulsed Cooling In High-Speed Thermoelectric Microcoolers, Bjorn Vermeersch, Je-Hyeong Bahk, James Christofferson, Ali Shakouri Mar 2013

Thermoreflectance Imaging Of Sub 100 Ns Pulsed Cooling In High-Speed Thermoelectric Microcoolers, Bjorn Vermeersch, Je-Hyeong Bahk, James Christofferson, Ali Shakouri

Birck and NCN Publications

Miniaturized thin film thermoelectric coolers have received considerable attention as potential means to locally address hot spots in microprocessors. Given the highly dynamic workload in complex integrated circuits, the need arises for a thorough understanding of the high-speed thermal behavior of microcoolers. Although some prior work on transient Peltier cooling in pulsed operation is available, these studies mostly focus on theoretical modeling and typically deal with relatively large modules with time constants well into the millisecond range. In this paper, we present an extensive experimental characterization of 30 x 30 mu m(2) high-speed coplanar SiGe superlattice microcoolers subjected to 300 …

Go to article

Deuterium Uptake In Magnetic-Fusion Devices With Lithium-Conditioned Carbon Walls, P. S. Krstic, Jean Paul Allain, C. N. Taylor, J. Dadras, S. Maeda, K. Morokuma, J. Jakowski, A. Allouche, C. H. Skinner Mar 2013

Deuterium Uptake In Magnetic-Fusion Devices With Lithium-Conditioned Carbon Walls, P. S. Krstic, Jean Paul Allain, C. N. Taylor, J. Dadras, S. Maeda, K. Morokuma, J. Jakowski, A. Allouche, C. H. Skinner

Birck and NCN Publications

Lithium wall conditioning has lowered hydrogenic recycling and dramatically improved plasma performance in many magnetic-fusion devices. In this Letter, we report quantum-classical atomistic simulations and laboratory experiments that elucidate the roles of lithium and oxygen in the uptake of hydrogen in amorphous carbon. Surprisingly, we show that lithium creates a high oxygen concentration on a carbon surface when bombarded by deuterium. Furthermore, surface oxygen, rather than lithium, plays the key role in trapping hydrogen. DOI: 10.1103/PhysRevLett.110.105001

Go to article

Laser Direct Writing Of Silicon Field Effect Transistor Sensors, Woongsik Nam, James I. Mitchell, Chookiat Tansarawiput, Minghao Qi, Xianfan Xu Mar 2013

Laser Direct Writing Of Silicon Field Effect Transistor Sensors, Woongsik Nam, James I. Mitchell, Chookiat Tansarawiput, Minghao Qi, Xianfan Xu

Birck and NCN Publications

We demonstrate a single step technique to fabricate silicon wires for field effect transistor sensors. Boron-doped silicon wires are fabricated using laser direct writing in combination with chemical vapor deposition, which has the advantages of precise control of position, orientation, and length, and in situ doping. The silicon wires can be fabricated to have very rough surfaces by controlling laser operation parameters, and thus, have large surface areas, enabling high sensitivity for sensing. Highly sensitive pH sensing is demonstrated. We expect our method can be expanded to the fabrication of various sensing devices beyond chemical sensors. (C) 2013 American Institute …

Go to article

Thermal Transport In Sige Superlattice Thin Films And Nanowires: Effects Of Specimen And Periodic Lengths, Keng-Hua Lin, Alejandro Strachan Mar 2013

Thermal Transport In Sige Superlattice Thin Films And Nanowires: Effects Of Specimen And Periodic Lengths, Keng-Hua Lin, Alejandro Strachan

Birck and NCN Publications

We compute the thermal conductivity of superlattice (SL) thin films and nanowires for various SL periods and total specimen lengths using nonequilibrium molecular dynamics. Both types of materials exhibit similar behaviors with respect to SL period but the thermal conductivity of the thin films exhibits a significantly higher sensitivity to the specimen length. Notably, the thermal conductivity of SL thin films is smaller than those of the corresponding nanowires for specimen lengths below approximately 35 nm. These results arise from the complex dependence of the conductivities of the interfaces and the SL components on the specimen size and period. These …

Go to article

First Prev Next Last