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Articles 61 - 72 of 72
Full-Text Articles in Nanoscience and Nanotechnology
Power Handling Of Electrostatic Mems Evanescent-Mode (Eva) Tunable Bandpass Filters, Xiaoguang Liu, Linda P.B. Katehi, William J. Chappell, Dimitrios Peroulis
Power Handling Of Electrostatic Mems Evanescent-Mode (Eva) Tunable Bandpass Filters, Xiaoguang Liu, Linda P.B. Katehi, William J. Chappell, Dimitrios Peroulis
Birck and NCN Publications
This paper presents the first theoretical and experimental study on the power handling capabilities of electrostatically tunable MEMS cavity filters. The theoretical analysis indicates that the frequency-dependent RF voltage inside a narrow-band filter may play an important role in the generation of electromechanical nonlinearities such as frequency response distortion, frequency shift, and bifurcation instability. This analysis also reveals that the filter's power handling capability is dependent on several critical factors, including the capacitive gap, stiffness of the diaphragm actuator, and the overall quality factor (Q) of the evanescent-mode (EVA) resonators. A nonlinear computer-aided design (CAD) model is proposed as a …
An All-Silicon Passive Optical Diode, Li Fan, Jian Wang, Leo T. Varghese, Hao Shen, Ben Niu, Yi Xuan, Andrew M. Weiner, Minghao Qi
An All-Silicon Passive Optical Diode, Li Fan, Jian Wang, Leo T. Varghese, Hao Shen, Ben Niu, Yi Xuan, Andrew M. Weiner, Minghao Qi
Birck and NCN Publications
A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input power is higher than the forward input. The silicon optical diode is ultracompact and is compatible with current complementary metal-oxide semiconductor processing.
Size Effects In Niti From Density Functional Theory Calculations, Karthik Guda Vishnu, Alejandro Strachan
Size Effects In Niti From Density Functional Theory Calculations, Karthik Guda Vishnu, Alejandro Strachan
Birck and NCN Publications
We use density functional theory to characterize how size affects the relative stability of thin NiTi slabs of different crystal structures and its implication on the martensitic phase transition that governs shape memory. We calculate the surface energies of B2' phase (austenite), B19 (orthorhombic), B19' (martensite), and a body-centered orthorhombic phase, the theoretically predicted ground state. We find that (110)(B2) surfaces with in-plane atomic displacements stabilize the austenite phase with respect to B19' and BCO; thus, slabs with such orientations are predicted to exhibit a decrease in martensite transition temperature with decreasing thickness. Our calculations predict a critical thickness of …
Resolving Structure And Mechanical Properties At The Nanoscale Of Viruses With Frequency Modulation Atomic Force Microscopy, David Martinez-Martin, Carolina Carrasco, Mercedes Hernando-Perez, Pedro J. De Pablo, Julio Gomez-Herrero, Rebeca Perez, Mauricio G. Mateu, Jose L. Carrascosa, Daniel Kiracofe, John Melcher, Arvind Raman
Resolving Structure And Mechanical Properties At The Nanoscale Of Viruses With Frequency Modulation Atomic Force Microscopy, David Martinez-Martin, Carolina Carrasco, Mercedes Hernando-Perez, Pedro J. De Pablo, Julio Gomez-Herrero, Rebeca Perez, Mauricio G. Mateu, Jose L. Carrascosa, Daniel Kiracofe, John Melcher, Arvind Raman
Birck and NCN Publications
Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images …
Energy-Based Yield Criterion For Pmma From Large-Scale Molecular Dynamics Simulations, Eugenio Jaramillo, Nathaniel Wilson, Stephen Christensen, Jonathan Gosse, Alejandro Strachan
Energy-Based Yield Criterion For Pmma From Large-Scale Molecular Dynamics Simulations, Eugenio Jaramillo, Nathaniel Wilson, Stephen Christensen, Jonathan Gosse, Alejandro Strachan
Birck and NCN Publications
We use molecular dynamics (MD) with the DREIDING force field to characterize the ultimate mechanical response of amorphous poly(methyl methacrylate). We characterize how volumetric and deviatoric strains contribute to yield for a wide range of loading conditions from pure deviatoric, volume-conserving cases to isotropic volume expansion. We propose and apply an energy-based yield criterion to define yield consistently for all cases. Our results show that permanent deformation occurs when either the deviatoric or volumetric strains reach critical values, except in a narrow region around the transformation between deviatoric- and volumetric-dominated yield where the two strain invariants interact. In contrast, the …
Optimization Of Power And Efficiency Of Thermoelectric Devices With Asymmetric Thermal Contacts, Kazuaki Yazawa, Ali Shakouri
Optimization Of Power And Efficiency Of Thermoelectric Devices With Asymmetric Thermal Contacts, Kazuaki Yazawa, Ali Shakouri
Birck and NCN Publications
We report the theoretical efficiency of thermoelectric power generation with asymmetric thermal contacts to reservoirs. A key ingredient is the electrical and thermal co-optimization. Generic formula of the maximum power output and the optimum leg length are obtained. The Curzon-Ahlborn limit at maximum power can be rigorously derived when the dimensionless figure-of-merit is very large for any asymmetric thermal contact resistances. The results differ from cyclic thermodynamic engines, and some of the reasons are discussed. We also point out the similarity and differences with single-level quantum dot heat engines, which assume no explicit thermal contact resistance with reservoirs. (C) 2012 …
Computational Study Of Energy Filtering Effects In One-Dimensional Composite Nano-Structures, Raseong Kim, Mark S. Lundstrom
Computational Study Of Energy Filtering Effects In One-Dimensional Composite Nano-Structures, Raseong Kim, Mark S. Lundstrom
Birck and NCN Publications
Possibilities to improve the Seebeck coefficient S versus electrical conductance G trade-off of diffusive composite nano-structures are explored using an electro-thermal simulation framework based on the non-equilibrium Green's function method for quantum electron transport and the lattice heat diffusion equation. We examine the role of the grain size d, potential barrier height Phi(B), grain doping, and the lattice thermal conductivity kappa(L) using a one-dimensional model structure. For a uniform kappa(L), simulation results show that the power factor of a composite structure may be improved over bulk with the optimum Phi(B) being about k(B)T, where k(B) and T are the Boltzmann …
Quantum-Hall Plateau-Plateau Transition In Top-Gated Epitaxial Graphene Grown On Sic (0001), T. Shen, A. T. Neal, M. L. Bolen, Jiangjiang Gu, L. W. Engel, Michael A. Capano, Peide D. Ye
Quantum-Hall Plateau-Plateau Transition In Top-Gated Epitaxial Graphene Grown On Sic (0001), T. Shen, A. T. Neal, M. L. Bolen, Jiangjiang Gu, L. W. Engel, Michael A. Capano, Peide D. Ye
Birck and NCN Publications
We investigate the low-temperature magneto-transport properties of monolayer epitaxial graphene films formed on the Si-face of semi-insulating 4H SiC substrates by a high-temperature sublimation process. A high-k top-gate on the epitaxial graphene is realized by inserting a fully oxidized nanometer-thin aluminum film as a seeding layer, followed by an atomic layer deposition process. At low temperatures, the devices demonstrate a strong field effect by the top gate with an on/off ratio of similar to 7 and an electron mobility up to similar to 3250 cm(2)/Vs. After the observation of the half-integer quantum-Hall effect for monolayer epitaxial graphene films, detailed magneto-transport …
Laser Direct Growth Of Graphene On Silicon Substrate, Dapeng Wei, Xianfan Xu
Laser Direct Growth Of Graphene On Silicon Substrate, Dapeng Wei, Xianfan Xu
Birck and NCN Publications
We demonstrate laser direct growth of few layer graphene on a silicon substrate. In our study, a continuous wave laser beam was focused on a poly(methyl methacrylate) (PMMA)-coated silicon wafer to evaporate PMMA and melt the silicon wafer. Carbon atoms, decomposed from PMMA, were absorbed by the molten silicon surface, and then separated from silicon in the cooling process to form few-layer graphene. This Si-catalyzed method will provide a new approach and platform for applications of graphene. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675636]
Full Band Atomistic Modeling Of Homo-Junction Ingaas Band-To-Band Tunneling Diodes Including Band Gap Narrowing, Woo-Suhl Cho, Mathieu Luisier, Dheeraj Mohata, Suman Datta, David Pawlik, Sean L. Rommel, Gerhard Klimeck
Full Band Atomistic Modeling Of Homo-Junction Ingaas Band-To-Band Tunneling Diodes Including Band Gap Narrowing, Woo-Suhl Cho, Mathieu Luisier, Dheeraj Mohata, Suman Datta, David Pawlik, Sean L. Rommel, Gerhard Klimeck
Birck and NCN Publications
A homo-junction In0.53Ga0.47As tunneling diode is investigated using full-band, atomistic quantum transport approach based on a tight-binding model (TB) and the Non-equilibrium Green’s Function formalism. Band gap narrowing (BGN) is included in TB by altering its parameters using the Jain-Roulston model. BGN is found to be critical in the determination of the current peak and the second turn-on in the forward bias region. An empirical excess current that mimics additional recombination paths must be added to the calculation to model the diode behavior in the valley current region. Overall the presented model reproduces experimental data well.
Feasibility, Accuracy, And Performance Of Contact Block Reduction Method For Multi-Band Simulations Of Ballistic Quantum Transport, Hoon Ryu, Hong-Hyun Park, Mincheol Shin, Dragica Vasileska, Gerhard Klimeck
Feasibility, Accuracy, And Performance Of Contact Block Reduction Method For Multi-Band Simulations Of Ballistic Quantum Transport, Hoon Ryu, Hong-Hyun Park, Mincheol Shin, Dragica Vasileska, Gerhard Klimeck
Birck and NCN Publications
Numerical utilities of the contact block reduction (CBR) method in evaluating the retarded Green’s function are discussed for 3D multi-band open systems that are represented by the atomic tight-binding (TB) and continuum k * p (KP) band model. It is shown that the methodology to approximate solutions of open systems, which has been already reported for the single-band effective mass model, cannot be directly used for atomic TB systems, since the use of a set of zinc blende crystal grids makes the inter-coupling matrix non-invertible. We derive and test an alternative with which the CBR method can be still practical …
Gaining Insight Into The Physics Of Dynamic Atomic Force Microscopy In Complex Environments Using The Veda Simulator, Daniel Kiracofe, John Melcher, Arvind Raman
Gaining Insight Into The Physics Of Dynamic Atomic Force Microscopy In Complex Environments Using The Veda Simulator, Daniel Kiracofe, John Melcher, Arvind Raman
Birck and NCN Publications
Dynamic atomic force microscopy (dAFM) continues to grow in popularity among scientists in many different fields, and research on new methods and operating modes continues to expand the resolution, capabilities, and types of samples that can be studied. But many promising increases in capability are accompanied by increases in complexity. Indeed, interpreting modern dAFM data can be challenging, especially on complicated material systems, or in liquid environments where the behavior is often contrary to what is known in air or vacuum environments. Mathematical simulations have proven to be an effective tool in providing physical insight into these non-intuitive systems. In …