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2010

Purdue University

Birck and NCN Publications

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Articles 1 - 30 of 38

Full-Text Articles in Nanoscience and Nanotechnology

Small-Scale Solutions To Grand Challenges In Thermal Management, Suresh V. Garimella Nov 2010

Small-Scale Solutions To Grand Challenges In Thermal Management, Suresh V. Garimella

Birck and NCN Publications

Research needs in the field of thermal management of microelectronics and microsystems are identified, followed by a brief discussion of recent advances in solution approaches. These include novel solutions that rely on two-phase flow at the microscale, micropumps, droplet actuation on structured surfaces, passive transport in wick structures, ion-driven and piezoelectrically driven airflow, nanostructured thermal materials, and novel diagnostic tools.

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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 Sep 2010

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 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 1D 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 CTAP is …

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Acoustic Phonon Scattering In Bi2te3/Sb2te3 Superlattices, Yaguo Wang, Carl Liebig, Xianfan Xu, Rama Venkatasubramanian Aug 2010

Acoustic Phonon Scattering In Bi2te3/Sb2te3 Superlattices, Yaguo Wang, Carl Liebig, Xianfan Xu, Rama Venkatasubramanian

Birck and NCN Publications

Ultrafast time-resolved measurements were conducted to investigate long-wavelength acoustic phonon scattering and velocity reduction in Bi2Te3/Sb2Te3 superlattices. We show that both these phenomena suppress heat transfer process, with the phonon scattering contributing more in differentiating the lattice thermal conductivities among films with different periods. Measurements of reduction in the acoustic phonon amplitudes support the decrease in the thermal conductivity for certain superlattice periods, which is not predicted by acoustic mismatch theory. This study is a direct measurement of coherent acoustic phonons in superlattices which is of significant interest to thermoelectrics.

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Eight-Channel Reconfigurable Microring Filters With Tunable Frequency, Extinction Ratio And Bandwidth, Hao Shen, Maroof H. Khan, Li Fan, Lin Zhao, Yi Xuan, Jing Ouyang, Leo T. Varghese, Minghao Qi Aug 2010

Eight-Channel Reconfigurable Microring Filters With Tunable Frequency, Extinction Ratio And Bandwidth, Hao Shen, Maroof H. Khan, Li Fan, Lin Zhao, Yi Xuan, Jing Ouyang, Leo T. Varghese, Minghao Qi

Birck and NCN Publications

We demonstrate an eight-channel reconfigurable optical filter on a silicon chip. It consists of cascaded microring resonators and integrated compact heaters. With an embedded Mach-Zehnder (MZ) arm coupling to a microring resonator, the important parameters of a filter such as center frequency, extinction ratio and bandwidth can be controlled simultaneously for purposes of filtering, routing and spectral shaping. Thus our device could potentially be useful in dense wavelength division multiplexing (DWDM) and radio frequency arbitrary waveform generation (RFAWG). Multichannel filter response was successfully tuned to match the International Telecommunication Unit (ITU) grid with 50, 100 and 200GHz in channel spacing. …

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Iii-Nitride Nanopyramid Light Emitting Diodes Grown By Organometallic Vapor Phase Epitaxy, Isaac Wildeson, Robert Colby, David Ewoldt, Zhiwen Liang, Dmitri Zakharov, Nestor J. Zaluzec, R. Edwin García, E A. Stach, Timothy D. Sands Aug 2010

Iii-Nitride Nanopyramid Light Emitting Diodes Grown By Organometallic Vapor Phase Epitaxy, Isaac Wildeson, Robert Colby, David Ewoldt, Zhiwen Liang, Dmitri Zakharov, Nestor J. Zaluzec, R. Edwin García, E A. Stach, Timothy D. Sands

Birck and NCN Publications

Nanopyramid light emitting diodes (LEDs) have been synthesized by selective area organometallic vapor phase epitaxy. Self-organized porous anodic alumina is used to pattern the dielectric growth e templates via reactive ion etching, eliminating the need for lithographic processes. (In,Ga)N quantum well growth occurs primarily on the six {1 (1) over bar 01} semipolar facets of each of the nanopyramids, while coherent (In,Ga)N quantum dots with heights of up to similar to 20 nm are incorporated at the apex by controlling growth conditions. Transmission electron microscopy (TEM) indicates that the (In,Ga)N active regions of the nanopyramid heterostructures are completely dislocation-free. Temperature-dependent …

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Microcantilever Dynamics In Liquid Environment Dynamic Atomic Force Microscopy When Using Higher-Order Cantilever Eigenmodes, Daniel Kiracofe, Arvind Raman Aug 2010

Microcantilever Dynamics In Liquid Environment Dynamic Atomic Force Microscopy When Using Higher-Order Cantilever Eigenmodes, Daniel Kiracofe, Arvind Raman

Birck and NCN Publications

Dynamic atomic force microscopy is currently evolving from a single to a multifrequency instrument for nanoscale imaging often employing higher-order microcantilever eigenmodes for improved resolution and force spectroscopy. In this work the authors study the fundamentals of cantilever dynamics and energy dissipation when soft cantilevers are driven at their second flexural eigenmode and interact with samples in liquid environments. Contrary to the conventional first eigenmode operation, second eigenmode operation in liquids is often dominated by a subharmonic response (e.g., one tap every four drive cycles) and there is an energy transfer to the first eigenmode creating a new channel of …

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Metric Signature Transitions In Optical Metamaterials, Igor Smolyaninov, Evgenii Narimanov Aug 2010

Metric Signature Transitions In Optical Metamaterials, Igor Smolyaninov, Evgenii Narimanov

Birck and NCN Publications

We demonstrate that the extraordinary waves in indefinite metamaterials experience an (- - + +) effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories.

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Current Density And Continuity In Discretized Models, Timothy B. Boykin, Mathieu Luisier, Gerhard Klimeck Jul 2010

Current Density And Continuity In Discretized Models, Timothy B. Boykin, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schr ¨ odinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying discrete models, students can encounter conceptual difficulties with the representation of the current and its divergence because different finite-difference expressions, all of which reduce to the current density in the continuous limit, measure different physical quantities. Understanding these different discrete currents is essential and requires a careful analysis of …

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High Performance Atomic-Layer-Deposited Laluo3/Ge-On-Insulator P-Channel Metal-Oxide-Semiconductor Field-Effect Transistor With Thermally Grown Geo2 As Interfacial Passivation Layer, J J. Gu, Y Q. Liu, M Xu, G K. Celler, R G. Gordon, P. D. Ye Jul 2010

High Performance Atomic-Layer-Deposited Laluo3/Ge-On-Insulator P-Channel Metal-Oxide-Semiconductor Field-Effect Transistor With Thermally Grown Geo2 As Interfacial Passivation Layer, J J. Gu, Y Q. Liu, M Xu, G K. Celler, R G. Gordon, P. D. Ye

Birck and NCN Publications

Enhancement-mode p-channel metal-oxide-semiconductor field-effect transistor (MOSFET) on germanium-on-insulator substrate is fabricated with atomic-layer-deposited (ALD) LaLuO3 as gate dielectric. Significant improvement in both on-state current and effective hole mobility has been observed for devices with thermal GeO2 passivation. The negative threshold voltage (V-T) shift in devices with GeO2 interfacial layer (IL) further demonstrates the effectiveness of surface passivation. Results from low temperature mobility characterization show that phonon scattering is the dominant scattering mechanism at a large inversion charge, indicating good interface quality. The combination of higher-k LaLuO3 and ultrathin GeO2 IL is a promising solution to the tradeoff between the aggressive …

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The Impact Of Nonlinearity On Degenerate Parametric Amplifiers, Jeff Rhoads, Steven W. Shaw Jun 2010

The Impact Of Nonlinearity On Degenerate Parametric Amplifiers, Jeff Rhoads, Steven W. Shaw

Birck and NCN Publications

This work investigates the effects of system nonlinearities on degenerate parametric amplifiers. A simple, Duffing-type nonlinearity is appended to a representative equation of motion for a mechanical or electromechanical parametric amplifier, and classical perturbation methods are used to characterize the resulting effects on the amplifier's frequency response and performance. Ultimately, the work demonstrates that parametric amplification can be realized in nonlinear, dynamic-range limited systems, such as resonant micro-or nanosystems, but at the expense of performance degradation. Additionally, it is shown that nonlinear amplifiers can be operated above their linear instability threshold but that doing so results in bistable amplified responses.

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Ambipolar Graphene Field Effect Transistors By Local Metal Side Gates, J F. Tian, L A. Jauregui, G Lopez, H Cao, Yong P. Chen Jun 2010

Ambipolar Graphene Field Effect Transistors By Local Metal Side Gates, J F. Tian, L A. Jauregui, G Lopez, H Cao, Yong P. Chen

Birck and NCN Publications

We demonstrate ambipolar graphene field effect transistors individually controlled by local metal side gates. The side gated field effect can have on/off ratio comparable with that of the global back gate, and can be tuned in a large range by the back gate and/or a second side gate. We also find that the side gated field effect is significantly stronger by electrically floating the back gate compared to grounding the back gate, consistent with the finding from electrostatic simulation.

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On The Bandstructure Velocity And Ballistic Current Of Ultra-Narrow Silicon Nanowire Transistors As A Function Of Cross Section Size, Orientation, And Bias, Neophytos Neophytou, Sung-Geun Kim, Gerhard Klimeck, Hans Kosina Jun 2010

On The Bandstructure Velocity And Ballistic Current Of Ultra-Narrow Silicon Nanowire Transistors As A Function Of Cross Section Size, Orientation, And Bias, Neophytos Neophytou, Sung-Geun Kim, Gerhard Klimeck, Hans Kosina

Birck and NCN Publications

A 20 band sp(3)d(5)s* spin-orbit-coupled, semiempirical, atomistic tight-binding model is used with a semiclassical, ballistic field-effect-transistor model, to theoretically examine the bandstructure carrier velocity and ballistic current in silicon nanowire (NW) transistors. Infinitely long, uniform, cylindrical, and rectangular NWs, of cross sectional diameters/sides ranging from 3-12 nm are considered. For a comprehensive analysis, n-type and p-type metal-oxide semiconductor (NMOS and PMOS) NWs in [100], [110], and [111] transport orientations are examined. In general, physical cross section reduction increases velocities, either by lifting the heavy mass valleys or significantly changing the curvature of the bands. The carrier velocities of PMOS [110] …

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Higher-Order Eigenmodes Of Qplus Sensors For High Resolution Dynamic Atomic Force Microscopy, Ryan C. Tung, Thorsten Wutscher, David Martinez-Martin, R. Reifenberger, Franz Giessibl, Arvind Raman May 2010

Higher-Order Eigenmodes Of Qplus Sensors For High Resolution Dynamic Atomic Force Microscopy, Ryan C. Tung, Thorsten Wutscher, David Martinez-Martin, R. Reifenberger, Franz Giessibl, Arvind Raman

Birck and NCN Publications

The time response of tuning-fork based sensors can be improved by operating them at higher eigenmodes because a measurement takes at least one oscillation cycle in dynamic force microscopy and the oscillation period of the second eigenmode is only about one sixth of the fundamental mode. Here we study the higher-order eigenmodes of quartz qPlus sensors [Bettac et al., Nanotechnology 20, 264009 (2009); Giessibl and Reichling, Nanotechnology 16, S118 (2005); Giessibl, Appl. Phys. Lett. 76, 1470 (2000); and Giessibl, Appl. Phys. Lett. 73, 3956 (1998)], their equivalent stiffness, and piezoelectric sensitivity, while paying special attention to the influence of the …

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Nanoscale Metal-Metal Contact Physics From Molecular Dynamics: The Strongest Contact Size, Hojin Kim, Alejandro Strachan May 2010

Nanoscale Metal-Metal Contact Physics From Molecular Dynamics: The Strongest Contact Size, Hojin Kim, Alejandro Strachan

Birck and NCN Publications

Using molecular dynamics we find that the tensile strength of the contacts between two clean platinum surfaces with nanoscale asperities is strongly size dependent with a maximum strength for contact lengths of approximately 5 nm. This is the first time a strongest size is observed in single crystals. The strengthening with decreasing size down to 5 nm results from a decrease in the initial density of mobile dislocations available for plastic deformation and the subsequent weakening originates from a reduction in the constraint to mechanical deformation inside the contact by the bulk.

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Extraordinary Transmission From High-Gain Nanoaperture Antennas, Edward C. Kinzel, Pornsak Srisungsitthisunti, Yan Li, Arvind Raman, Xianfan Xu May 2010

Extraordinary Transmission From High-Gain Nanoaperture Antennas, Edward C. Kinzel, Pornsak Srisungsitthisunti, Yan Li, Arvind Raman, Xianfan Xu

Birck and NCN Publications

This letter describes a bowtie nanoaperture antenna for coupling light to a subdiffraction limited near-field spot (<λ/8). The gain of the antenna is increased using a concentric grating structure to coherently diffract normally incident light toward the aperture. We experimentally demonstrate that the addition of the grating structure enhances the far-field transmission through the aperture by 6.9 times while the intensity at the near-field is increased more than 15 times. The nanoantenna is useful for applications including nanolithography and data storage.

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Experimental Observation Of The Trapped Rainbow, Vera N. Smolyaninova, Igor Smolyaninov, Alexander V. Kildishev, V. M. Shalaev May 2010

Experimental Observation Of The Trapped Rainbow, Vera N. Smolyaninova, Igor Smolyaninov, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We report on the experimental demonstration of the broadband "trapped rainbow" in the visible frequency range using an adiabatically tapered optical nano waveguide. Being a distinct case of the slow light phenomenon, the trapped rainbow effect could be applied to optical computing and signal processing, such as spectroscopy on a chip, and to providing enhanced light-matter interactions. (C) 2010 American Institute of Physics.

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Simulation Of Nanowire Tunneling Transistors: From The Wentzel-Kramers-Brillouin Approximation To Full-Band Phonon-Assisted Tunneling, Mathieu Luisier, Gerhard Klimeck Apr 2010

Simulation Of Nanowire Tunneling Transistors: From The Wentzel-Kramers-Brillouin Approximation To Full-Band Phonon-Assisted Tunneling, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Nanowire band-to-band tunneling field-effect transistors 􏰀TFETs􏰁 are simulated using the Wentzel– Kramers–Brillouin 􏰀WKB􏰁 approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling 􏰀PAT􏰁. It is found that the WKB approximation properly works if one single imaginary path connecting the valence band 􏰀VB􏰁 and the conduction band 􏰀CB􏰁 dominates the tunneling process as in direct band gap semiconductors. However, PAT is essential in Si and Ge nanowire TFETs where multiple, tightly-coupled, imaginary paths exist between the VB and the CB. © 2010 American Institute of Physics. 􏰂doi:10.1063/1.3386521􏰃

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Chaos-Assisted Directional Light Emission From Microcavity Lasers, Susumu Shinohara, Takahisa Harayama, Takehiro Fukushima, Martina Hentschel, Takahiko Sasaki, Evgenii Narimanov Apr 2010

Chaos-Assisted Directional Light Emission From Microcavity Lasers, Susumu Shinohara, Takahisa Harayama, Takehiro Fukushima, Martina Hentschel, Takahiko Sasaki, Evgenii Narimanov

Birck and NCN Publications

We study the effect of dynamical tunneling on emission from ray-chaotic microcavities by introducing a suitably designed deformed disk cavity. We focus on its high quality factor modes strongly localized along a stable periodic ray orbit confined by total internal reflection. It is shown that dominant emission originates from the tunneling from the periodic ray orbit to chaotic ones; the latter eventually escape from the cavity refractively, resulting in directional emission that is unexpected from the geometry of the periodic orbit, but fully explained by unstable manifolds of chaotic ray dynamics. Experimentally performing selective excitation of those modes, we succeeded …

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Computational Study Of An Ingan/Gan Nanocolumn Light-Emitting Diode, Christoph Boecklin, Ratko G. Veprek, Sebastian Steiger, Bernd Witzigmann Apr 2010

Computational Study Of An Ingan/Gan Nanocolumn Light-Emitting Diode, Christoph Boecklin, Ratko G. Veprek, Sebastian Steiger, Bernd Witzigmann

Birck and NCN Publications

A comprehensive three-dimensional analysis of the operation of an In0.4Ga0.6N/GaN nanocolumn light-emitting diode is presented. Focus is put on the investigation of the nature and location of the emitting states. Calculations of strain and polarization-induced internal fields show that the strong lateral dependence of the potential gives rise to states confined to the periphery and to the center of the nanocolumn. However, lateral confinement of states near the column center is weak such that a quantum-well-like treatment of the remaining bound states seems appropriate where coherence is lost in the lateral directions. Within this picture, a coupled and self-consistent three-dimensional …

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Fabrication Of Conductive Interconnects By Ag Migration In Cu-Ag Core-Shell Nanoparticles, Suk Jun Kim, E A. Stach, Carol A. Handwerker Apr 2010

Fabrication Of Conductive Interconnects By Ag Migration In Cu-Ag Core-Shell Nanoparticles, Suk Jun Kim, E A. Stach, Carol A. Handwerker

Birck and NCN Publications

Fabrication of conductive nanoparticle films is observed in Cu-Ag core-shell nanoparticles by fast diffusion of Ag at 220 degrees C from particle surfaces, leading to the formation of sintered necks of Ag at the initial particle-particle contacts. Transmission electron microscopy showed that the necks were pure Ag and that particle surfaces away from the contacts were nearly Ag-free. The extent of neck formation is controllable by the choice of initial Ag thickness. Analysis of the thermodynamics of the Ag-Cu system and the relative diffusivities of Ag and Cu provide criteria for fabrication of other core-shell two-phase systems by the same …

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Strain-Induced, Off-Diagonal, Same-Atom Parameters In Empirical Tight-Binding Theory Suitable For [110] Uniaxial Strain Applied To A Silicon Parametrization, Timothy B. Boykin, Mathieu Luisier, Mehdi Salmani-Jelodar, Gerhard Klimeck Mar 2010

Strain-Induced, Off-Diagonal, Same-Atom Parameters In Empirical Tight-Binding Theory Suitable For [110] Uniaxial Strain Applied To A Silicon Parametrization, Timothy B. Boykin, Mathieu Luisier, Mehdi Salmani-Jelodar, Gerhard Klimeck

Birck and NCN Publications

State-of-the-art transistors achieve their improved performance through strain engineering. The somewhat unusual uniaxial [110] strain is of particular importance as it provides a significant mobility increase for electrons. Empirical tight binding has shown tremendous benefits in modeling realistically large structures including standard strain conditions, but often fails to predict the correct uniaxial [110] strain behavior because most treatments neglect the same-atom different-orbital matrix elements induced by this strain. Two separate mechanisms are responsible for these conditions: Loumlwdin orbital changes and displacement of nearest-neighbor potentials. We present a model which separately includes both mechanisms via parameters whose range of validity can …

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On Momentum Conservation And Thermionic Emission Cooling, Raseong Kim, Changwook Jeong, Mark S. Lundstrom Mar 2010

On Momentum Conservation And Thermionic Emission Cooling, Raseong Kim, Changwook Jeong, Mark S. Lundstrom

Birck and NCN Publications

The possibility of increasing the performance of thermionic cooling devices by relaxing lateral momentum conservation is examined. Upper limits for the ballistic emission current are established. It is then shown that for most cases, nonconserved lateral momentum model produces a current that exceeds this upper limit. For the case of heterojunctions with a much heavier effective mass in the barrier and with a low barrier height, however, relaxing lateral momentum may increase the current. These results can be simply understood from the general principle that the current is limited by the location, well or barrier, with the smallest number of …

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Communications: Entanglement Switch For Dipole Arrays, Qi Wei, Sabre Kais, Yong P. Chen Mar 2010

Communications: Entanglement Switch For Dipole Arrays, Qi Wei, Sabre Kais, Yong P. Chen

Birck and NCN Publications

We propose a new entanglement switch of qubits consisting of electric dipoles oriented along or against an external electric field and coupled by the electric dipole-dipole interaction. The pairwise entanglement can be tuned and controlled by the ratio of the Rabi frequency and the dipole-dipole coupling strength. Tuning the entanglement can be achieved for one, two, and three-dimensional arrangements of the qubits. The feasibility of building such an entanglement switch is also discussed.

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Electronic Transport In Chemical Vapor Deposited Graphene Synthesized On Cu: Quantum Hall Effect And Weak Localization, Helin Cao, Qingkai Yu, Luis A. Jauregui, J Tian, W Wu, Z Liu, Ramaneh Jalilian, D K. Benjamin, Z Jiang, J Bao, S S. Pei, Yong P. Chen Mar 2010

Electronic Transport In Chemical Vapor Deposited Graphene Synthesized On Cu: Quantum Hall Effect And Weak Localization, Helin Cao, Qingkai Yu, Luis A. Jauregui, J Tian, W Wu, Z Liu, Ramaneh Jalilian, D K. Benjamin, Z Jiang, J Bao, S S. Pei, Yong P. Chen

Birck and NCN Publications

We report on electronic properties of graphene synthesized by chemical vapor deposition (CVD) on copper then transferred to SiO2/Si. Wafer-scale (up to 4 in.) graphene films have been synthesized, consisting dominantly of monolayer graphene as indicated by spectroscopic Raman mapping. Low temperature transport measurements are performed on microdevices fabricated from such CVD graphene, displaying ambipolar field effect (with on/off ratio similar to 5 and carrier mobilities up to similar to 3000 cm(2)/V s) and "half-integer" quantum Hall effect, a hall-mark of intrinsic electronic properties of monolayer graphene. We also observe weak localization and extract information about phase coherence and scattering …

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Note: Thermal Analog To Atomic Force Microscopy Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John Blendell, Suresh Garimella Mar 2010

Note: Thermal Analog To Atomic Force Microscopy Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John Blendell, Suresh Garimella

Birck and NCN Publications

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.

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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 Feb 2010

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 …

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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 Feb 2010

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.

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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 Feb 2010

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 …

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Exact Calculation Of Entanglement In A 19-Site Two-Dimensional Spin System, Qing Xu, Sabre Kais, Maxim Naumov, Ahmed Sameh Feb 2010

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 …

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On Eigenmodes, Stiffness, And Sensitivity Of Atomic Force Microscope Cantilevers In Air Versus Liquids, Daniel Kiracofe, Arvind Raman Feb 2010

On Eigenmodes, Stiffness, And Sensitivity Of Atomic Force Microscope Cantilevers In Air Versus Liquids, Daniel Kiracofe, Arvind Raman

Birck and NCN Publications

The effect of hydrodynamic loading on the eigenmode shapes, modal stiffnesses, and optical lever sensitivities of atomic force microscope (AFM) microcantilevers is investigated by measuring the vibrations of such microcantilevers in air and water using a scanning laser Doppler vibrometer. It is found that for rectangular tipless microcantilevers, the measured fundamental and higher eigenmodes and their equivalent stiffnesses are nearly identical in air and in water. However, for microcantilevers with a tip mass or for picket shaped cantilevers, there is a marked difference in the second (and higher) eigenmode shapes between air and water that leads to a large decrease …

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