Nanoscience and Nanotechnology | Open Access Articles

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 …

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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 …

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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 …

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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 …

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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 …

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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 …

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Molecular Dynamics Characterization Of The Contact Between Clean Metallic Surfaces With Nanoscale Asperities, Hojin Kim, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics (MD) simulations to characterize the tensile strength of contacts formed between various clean platinum surfaces with nanoscale asperities. Both commensurate contacts between (001) and (111) surfaces and incommensurate (001) ones are considered over a wide range of asperity sizes. In cyclic closing and opening, fresh asperities that form contacts for the first time show significant plastic deformation; this leads to a reduction in the effective contact area during the first few cycles, after which steady state is achieved both in terms of contact size and the pull-out force necessary to open the contacts. As is the …

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Lattice Thermal Conductivity Reduction In Bi2te3 Quantum Wires With Smooth And Rough Surfaces: A Molecular Dynamics Study, Bo Qiu, Lin Sun, Xiulin Ruan

Birck and NCN Publications

Using molecular dynamics simulations, we have predicted the thermal conductivity of Bi2Te3 nanowires with diameters ranging from 3 to 30 nm with both smooth and rough surfaces. It is found that when the nanowire diameter decreases to the molecular scale (below 10 nm, or the so-called "quantum wire"), the thermal conductivity shows significant reduction as compared to bulk value. On the other hand, the thermal conductivity for the 30-nm-diam nanowire only shows less than 20% reduction, in agreement with recent experimental data. Also, the thermal conductivity of nanowires shows a weaker temperature dependence than the typical T-1 trend, consistent with …

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Phonon-Limited And Effective Low-Field Mobility In N- And P-Type [100]-, [110]-, And [111]-Oriented Si Nanowire Transistors, Mathieu Luisier

Birck and NCN Publications

Ultrascaled n- and p-type Si nanowire field-effect transistors (NW FETs) with [100], [110], and [111] as channel orientations are simulated in the presence of electron-phonon scattering using an atomistic quantum transport solver based on the sp(3)d(5)s* tight-binding model for electrons and holes, a modified Keating model for phonons, and the nonequilibrium Green's function formalism. The channel resistances of devices with different gate lengths and carrier concentrations are computed at room temperature and used to extract phonon-limited, ballistic, and effective low-field mobilities. It is found that a [110] channel represents the best choice for high n- and p-type NW FET performances. …

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Effect Of Strain On Stripe Phases In The Quantum Hall Regime, Sunanda P. Koduvayur, Yuli Lyanda-Geller, Sergei Khlebnikov, Gabor Csathy, Michael J. Manfra, Loren N. Pfeiffer, Kenneth W. West, Leonid P. Rokhinson

Birck and NCN Publications

Preferential orientation of the stripe phases in the quantum Hall (QH) regime has remained a puzzle since its discovery. We show experimentally and theoretically that the direction of high and low resistance of the two-dimensional (2D) hole gas in the QH regime can be controlled by an external strain. Depending on the sign of the in-plane shear strain, the Hartree-Fock energy of holes or electrons is minimized when the charge density wave (CDW) is oriented along the [110] or [1 (1) over bar0] directions. We suggest that shear strains due to internal electric fields in the growth direction are responsible …

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Effects Of Interface Disorder On Valley Splitting In Sige/Si/Sige Quantum Wells, Zhengping Jiang, Neerav Kharche, Timothy Boykin, Gerhard Klimeck

Birck and NCN Publications

A sharp potential barrier at the Si/SiGe interface introduces valley splitting (VS), which lifts the 2-fold valley degeneracy in strained SiGe/Si/SiGe quantum wells (QWs). This work examines in detail the effects of Si/SiGe interface disorder on the VS in an atomistic tight binding approach based on statistical sampling. VS is analyzed as a function of electric field, QW thickness, and simulation domain size. Strong electric fields push the electron wavefunctions into the SiGe buffer and introduce significant VS fluctuations from device to device. A Gedankenexperiment with ordered alloys sheds light on the importance of different bonding configurations on VS. We …

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Influence Of Cross-Section Geometry And Wire Orientation On The Phonon Shifts In Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Engineering of the cross-section shape and size of ultra-scaled Si nanowires (SiNWs) provides an attractive way for tuning their structural properties. The acoustic and optical phonon shifts of the free-standing circular, hexagonal, square and triangular SiNWs are calculated using a Modified Valence Force Field (MVFF) model. The acoustic phonon blue shift (acoustic hardening) and the optical phonon red shift (optical softening) show a strong dependence on the cross-section shape and size of the SiNWs. The triangular SiNWs have the least structural symmetry as revealed by the splitting of the degenerate flexural phonon modes and The show the minimum acoustic hardening …

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Shape And Orientation Effects On The Ballistic Phonon Thermal Properties Of Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

The effect of geometrical confinement, atomic position and orientation of Silicon nanowires (SiNWs) on their thermal properties are investigated using the phonon dispersion obtained using a Modified Valence Force Field (MVFF) model. The spe- cific heat (Cv) and the ballistic thermal conductance (κbal) shows anisotropic variation l with changing cross-section shape and size of the SiNWs. The Cv increases with de- creasing cross-section size for all the wires. The triangular wires show the largest Cv due to their highest surface-to-volume ratio. The square wires with [110] orientation show the maximum κbal since they have the highest number of conducting phonon …

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Effects Of Interface Roughness Scattering On Radio Frequency Performance Of Silicon Nanowire Transistors, Sunggeun Kim, Mathieu Luisier, Timothy B. Boykin, Gerhard Klimeck

Birck and NCN Publications

The effects of an atomistic interface roughness in n-type silicon nanowire transistors (SiNWT) on the radio frequency performance are analyzed. Interface roughness scattering (IRS) is statistically investigated through a three dimensional full–band quantum transport simulation based on the sp3d5s∗ tight–binding model. As the diameter of the SiNWT is scaled down below 3 nm, IRS causes a significant reduction of the cut-off frequency. The fluctuations of the conduction band edge due to the rough surface lead to a reflection of electrons through mode-mismatch. This effect reduces the velocity of electrons and hence the transconductance considerably causing a cut-off frequency reduction.

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Full-Text Articles in Nanoscience and Nanotechnology

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

Molecular Dynamics Characterization Of The Contact Between Clean Metallic Surfaces With Nanoscale Asperities, Hojin Kim, Alejandro Strachan

Birck and NCN Publications

Lattice Thermal Conductivity Reduction In Bi2te3 Quantum Wires With Smooth And Rough Surfaces: A Molecular Dynamics Study, Bo Qiu, Lin Sun, Xiulin Ruan

Birck and NCN Publications

Phonon-Limited And Effective Low-Field Mobility In N- And P-Type [100]-, [110]-, And [111]-Oriented Si Nanowire Transistors, Mathieu Luisier

Birck and NCN Publications

Effect Of Strain On Stripe Phases In The Quantum Hall Regime, Sunanda P. Koduvayur, Yuli Lyanda-Geller, Sergei Khlebnikov, Gabor Csathy, Michael J. Manfra, Loren N. Pfeiffer, Kenneth W. West, Leonid P. Rokhinson

Birck and NCN Publications

Effects Of Interface Disorder On Valley Splitting In Sige/Si/Sige Quantum Wells, Zhengping Jiang, Neerav Kharche, Timothy Boykin, Gerhard Klimeck

Birck and NCN Publications

Influence Of Cross-Section Geometry And Wire Orientation On The Phonon Shifts In Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Shape And Orientation Effects On The Ballistic Phonon Thermal Properties Of Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Effects Of Interface Roughness Scattering On Radio Frequency Performance Of Silicon Nanowire Transistors, Sunggeun Kim, Mathieu Luisier, Timothy B. Boykin, Gerhard Klimeck

Birck and NCN Publications