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Full-Text Articles in Nanoscience and Nanotechnology

Thermal Transport At The Nanoscale: A Fourier's Law Vs. Phonon Boltzmann Equation Study, Jan Kaiser, T. Feng, Jesse Maassen, X. Wang, X. Ruan, Mark S. Lundstrom Jan 2017

Thermal Transport At The Nanoscale: A Fourier's Law Vs. Phonon Boltzmann Equation Study, Jan Kaiser, T. Feng, Jesse Maassen, X. Wang, X. Ruan, Mark S. Lundstrom

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Steady-state thermal transport in nanostructures with dimensions comparable to the phonon mean-free-path is examined. Both the case of contacts at different temperatures with no internal heat generation and contacts at the same temperature with internal heat generation are considered. Fourier’s Law results are compared to finite volume method solutions of the phonon Boltzmann equation in the gray approximation. When the boundary conditions are properly specified, results obtained using Fourier’s Law without modifying the bulk thermal conductivity are in essentially exact quantitative agreement with the phonon Boltzmann equation in the ballistic and diffusive limits. The errors between these two ...


Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck, Hans Kosina Mar 2011

Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck, Hans Kosina

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Ultra-thin-body (UTB) channel materials of a few nanometers in thickness are currently considered as candidates for future electronic, thermoelectric, and optoelectronic applications. Among the features that they possess, which make them attractive for such applications, their confinement length scale, transport direction, and confining surface orientation serve as degrees of freedom for engineering their electronic properties. This work presents a comprehensive study of hole velocities in p-type UTB films of widths from 15 nm down to 3 nm. Various transport and surface orientations are considered. The atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used for the electronic structure, and a semiclassical ballistic ...


Universality Of Non-Ohmic Shunt Leakage In Thin-Film Solar Cells, Sourabh Dongaonkar, J. D. Servaites, G. M. Ford, S. Loser, R. M. Gelfand, H. Mohseni, Hugh Hillhouse, R. Agrawal, M. A. Ratner, T. J. Marks, Mark S. Lundstrom, Muhammad A. Alam Dec 2010

Universality Of Non-Ohmic Shunt Leakage In Thin-Film Solar Cells, Sourabh Dongaonkar, J. D. Servaites, G. M. Ford, S. Loser, R. M. Gelfand, H. Mohseni, Hugh Hillhouse, R. Agrawal, M. A. Ratner, T. J. Marks, Mark S. Lundstrom, Muhammad A. Alam

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We compare the dark current-voltage (IV) characteristics of three different thin-film solar cell types: hydrogenated amorphous silicon (a-Si:H) p-i-n cells, organic bulk heterojunction (BHJ) cells, and Cu(In, Ga)Se-2 (CIGS) cells. All three device types exhibit a significant shunt leakage current at low forward bias (V < similar to 0.4) and reverse bias, which cannot be explained by the classical solar cell diode model. This parasitic shunt current exhibits non-Ohmic behavior, as opposed to the traditional constant shunt resistance model for photovoltaics. We show here that this shunt leakage (I-sh), across all three solar cell types considered, is characterized by the following common phenomenological features: (a) voltage symmetry about V = 0, (b) nonlinear (power law) voltage dependence, and (c) extremely weak temperature dependence. Based on this analysis, we provide a simple method of subtracting this shunt current component from the measured data and discuss its implications on dark IV parameter extraction. We propose a space charge limited (SCL) current model for capturing all these features of the shunt leakage in a consistent framework and discuss possible physical origin of the parasitic paths responsible for this shunt current mechanism. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518509]


A Domain Adaptive Stochastic Collocation Approach For Analysis Of Mems Under Uncertainties, Nitin Agarwal, N R. Aluru Nov 2009

A Domain Adaptive Stochastic Collocation Approach For Analysis Of Mems Under Uncertainties, Nitin Agarwal, N R. Aluru

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This work proposes a domain adaptive stochastic collocation approach for uncertainty quantification, suitable for effective handling of discontinuities or sharp variations in the random domain. The basic idea of the proposed methodology is to adaptively decompose the random domain into subdomains. Within each subdomain, a sparse grid interpolant is constructed using the classical Smolyak construction [S. Smolyak, Quadrature and interpo- lation formulas for tensor products of certain classes of functions, Soviet Math. Dokl. 4 (1963) 240–243], to approximate the stochastic solution locally. The adaptive strategy is governed by the hierarchical surpluses, which are computed as part of the interpolation ...


Strain Energy And Lateral Friction Force Distributions Of Carbon Nanotubes Manipulated Into Shapes By Atomic Force Microscopy, Mark C. Strus, Roya R. Lahiji, Pablo Ares, Vincente Lopez, Arvind Raman, Ron R. Reifenberger Aug 2009

Strain Energy And Lateral Friction Force Distributions Of Carbon Nanotubes Manipulated Into Shapes By Atomic Force Microscopy, Mark C. Strus, Roya R. Lahiji, Pablo Ares, Vincente Lopez, Arvind Raman, Ron R. Reifenberger

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The interplay between local mechanical strain energy and lateral frictional forces determines the shape of carbon nanotubes on substrates. In turn, because of its nanometer-size diameter, the shape of a carbon nanotube strongly influences its local electronic, chemical, and mechanical properties. Few, if any, methods exist for resolving the strain energy and static frictional forces along the length of a deformed nanotube supported on a substrate. We present a method using nonlinear elastic rod theory in which we compute the flexural strain energy and static frictional forces along the length of single walled carbon nanotubes (SWCNTs) manipulated into various shapes ...


Gold Nanorod-Mediated Photothermolysis Induces Apoptosis Of Macrophages Via Damage Of Mitochondria, Ling Tong, Ji-Xin Cheng Apr 2009

Gold Nanorod-Mediated Photothermolysis Induces Apoptosis Of Macrophages Via Damage Of Mitochondria, Ling Tong, Ji-Xin Cheng

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Aims: Induction of apoptosis or necrosis in activated macrophages by gold nanorod-mediated photothermolysis is demonstrated and the mechanisms underlying the processes are investigated. Materials & methods: Gold nanorods were functionalized with cysteine-octaarginine peptides (R8-NRs). Uptake of R8-NRs by activated macrophages was monitored by two-photon luminescence imaging. The laser irradiation conditions were controlled to induce apoptosis or necrosis to R8-NR-internalized macrophages. Mitochondrial damage and reactive oxygen species overproduction during photothermolysis was investigated by confocal fluorescence microscopy and transmission-electron microscopy. Results: Activated macrophages efficiently uptake R8-NRs both in vitro and in live animals. Laser irradiation of internalized nanorods with controlled power density induces ...


Interfacial Energy Between Carbon Nanotubes And Polymers Measured From Nanoscale Peel Tests In The Atomic Force Microscope, Mark C. Strus, Camilo I. Cano, R. Byron Pipes, Cattien V. Nguyen, Arvind Raman Mar 2009

Interfacial Energy Between Carbon Nanotubes And Polymers Measured From Nanoscale Peel Tests In The Atomic Force Microscope, Mark C. Strus, Camilo I. Cano, R. Byron Pipes, Cattien V. Nguyen, Arvind Raman

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The future development of polymer composite materials with nanotubes or nanoscale fibers requires the ability to understand and improve the interfacial bonding at the nanotube-polymer matrix interface. In recent work [Strus MC, Zalamea L, Raman A, Pipes RB, Nguyen CV, Stach EA. Peeling force spectroscopy: exposing the adhesive nanomechanics of one-dimensional nanostructures. Nano Lett 2008;8(2):544–50], it has been shown that a new mode in the Atomic Force Microscope (AFM), peeling force spectroscopy, can be used to understand the adhesive mechanics of carbon nanotubes peeled from a surface. In the present work, we demonstrate how AFM peeling ...


Imaging Gold Nanorods By Plasmon-Resonance-Enhanced Four Wave Mixing, Yookyung Jung, Hongtao Chen, Ling Tong, Ji-Xin Cheng Feb 2009

Imaging Gold Nanorods By Plasmon-Resonance-Enhanced Four Wave Mixing, Yookyung Jung, Hongtao Chen, Ling Tong, Ji-Xin Cheng

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The current work investigates the four-wave mixing (FWM) signal from gold nanorods (NRs) using two synchronized lasers and its potential applications in bioimaging. Using the lightning rod model, we show that the strongest FWM occurs when the pump laser wavelength is tuned to be resonant with the longitudinal plasmon resonance wavelength of NR. The calculation is experimentally demonstrated by comparing the intensities of FWM from NRs with different plasmon resonance wavelengths. The FWM signal is further found to be enhanced by aggregation of NRs and is strongly dependent on pulse width. The FWM intensity from NRs is similar to 39 ...


Gold Nanorods As Contrast Agents For Biological Imaging: Optical Properties, Surface Conjugation And Photothermal Effects, Ling Tong, Qingshan Wei, Alexander Wei, Ji-Xin Cheng Jan 2009

Gold Nanorods As Contrast Agents For Biological Imaging: Optical Properties, Surface Conjugation And Photothermal Effects, Ling Tong, Qingshan Wei, Alexander Wei, Ji-Xin Cheng

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Gold nanorods (NRs) have plasmon-resonant absorption and scattering in the near-infrared (NIR) region, making them attractive probes for in vitro and in vivo imaging. In the cellular environment, NRs can provide scattering contrast for darkfield microscopy, or emit a strong two-photon luminescence due to plasmon-enhanced two-photon absorption. NRs have also been employed in biomedical imaging modalities such as optical coherence tomography or photoacoustic tomography. Careful control over surface chemistry enhances the capacity of NRs as biological imaging agents by enabling cell-specific targeting, and by increasing their dispersion stability and circulation lifetimes. NRs can also efficiently convert optical energy into heat ...


Full-Band And Atomisic Simulation Of Realistic 40 Nm Inas Hemt, Mathieu Luisier, Neophytos Neophytou, Neerav Kharche, Gerhard Klimeck Dec 2008

Full-Band And Atomisic Simulation Of Realistic 40 Nm Inas Hemt, Mathieu Luisier, Neophytos Neophytou, Neerav Kharche, Gerhard Klimeck

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A realistic 40 nm InAs high electron mobility transistor is studied using a two-dimensional, full-band, and atomistic Schr¨odinger-Poisson solver based on the sp3d5s∗ tightbinding model. Bandstructure non-parabolicity effects, strain, alloy disorder in the InGaAs and InAlAs barriers, as well as band-to-band tunneling in the transistor OFF-state are automatically included through the full-band atomistic model. The source and drain contact extensions are taken into account a posteriori by adding two series resistances to the device channel. The simulated current characteristics are compared to measured data and show a good quantitative agreement.


Transport-Based Dopant Metrology In Advanced Finfets, Gabriel P. Lansbergen, Rajib Rahman, Cameron J. Wellard, Jaap Caro, Nadine Collaert, Serge Biesemans, Gerhard Klimeck, Lloyd C. L. Hollenberg, Sven Rogge Dec 2008

Transport-Based Dopant Metrology In Advanced Finfets, Gabriel P. Lansbergen, Rajib Rahman, Cameron J. Wellard, Jaap Caro, Nadine Collaert, Serge Biesemans, Gerhard Klimeck, Lloyd C. L. Hollenberg, Sven Rogge

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Ultra-scaled FinFET transistors bear unique fingerprint-like device-to-device differences attributed to random single impurities. Through correlation of experimental data with multimillion atom simulations in NEMO 3-D, we can identify the impurity’s chemical species and determine their concentration, local electric field and depth below the Si/SiO2 interface. The ability to model the excited states rather than just the ground states is the critical need. We therefore demonstrate a new approach to atomistic impurity metrology and confirm the assumption of tunneling through individual impurity quantum states.


From Nemo1d And Nemo3d To Omen: Moving Towards Atomistic 3-D Quantum Transport In Nano-Scale Semiconductors, Gerhard Klimeck, Mathieu Luisier Dec 2008

From Nemo1d And Nemo3d To Omen: Moving Towards Atomistic 3-D Quantum Transport In Nano-Scale Semiconductors, Gerhard Klimeck, Mathieu Luisier

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Lessons learned in 15 years of NEMO development starting from quantitative and predictive resonant tunneling diode (RTD) to multi-million atom electronic structure modeling and the path for OMEN are laid out. The recent OMEN capabilities enable realistically large 3D atomistic nano-scale device simulation.


Toward Nanowire Electronics, Joerg Appenzeller, Joachim Knoch, Mikael Bjoerk, Heike Riel, Heinz Schmid, Walter Riess Nov 2008

Toward Nanowire Electronics, Joerg Appenzeller, Joachim Knoch, Mikael Bjoerk, Heike Riel, Heinz Schmid, Walter Riess

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This paper discusses the electronic transport properties of nanowire field-effect transistors (NW-FETs). Four different device concepts are studied in detail: Schottky-barrier NW-FETs with metallic source and drain contacts, conventional-type NW-FETs with doped NW segments as source and drain electrodes, and, finally, two new concepts that enable steep turn-on characteristics, namely, NW impact ionization FETs and tunnel NW-FETs. As it turns out, NW-FETs are, to a large extent, determined by the device geometry, the dimensionality of the electronic transport, and the way of making contacts to the NW. Analytical as well as simulation results are compared with experimental data to explain ...


Level Spectrum Of Single Gated As Donors, Gabriel P. Lansbergen, Rajib Rahman, J. Caro, N. Collaert, S. Biesemans, Gerhard Klimeck, S. Rogge, L.C. L. Hollenberg Jul 2008

Level Spectrum Of Single Gated As Donors, Gabriel P. Lansbergen, Rajib Rahman, J. Caro, N. Collaert, S. Biesemans, Gerhard Klimeck, S. Rogge, L.C. L. Hollenberg

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We study the electrical transport through single As donors incorporated in the channel of a FinFET, i.e. a donor in a three-terminal geometry. By means of spectroscopic measurements in conjuction with a NEMO-3D model, we can identify the excited states and associate them with either the donors Coulomb potential, a triangular well at the interface or a hybridized combination of the two. The correspondence between the transport measurements, the theoretical model and the local environment provides an atomic understanding of actual gated donors in a nanostructure.


Release Of Hydrophobic Molecules From Polymer Micelles Into Cell Membranes Revealed By Forster Resonance Energy Transfer Imaging, Hongtao Chen, Sungwon Kim, Shuyi Wang, Kinam Park, Ji-Xin Cheng May 2008

Release Of Hydrophobic Molecules From Polymer Micelles Into Cell Membranes Revealed By Forster Resonance Energy Transfer Imaging, Hongtao Chen, Sungwon Kim, Shuyi Wang, Kinam Park, Ji-Xin Cheng

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it is generally assumed that polymeric micelles, upon administration into the blood stream, carry drug molecules until they are taken up into cells followed by intracellular release. The current work revisits this conventional wisdom. The study using dual-labeled micelles containing fluorescently labeled copolymers and hydrophobic fluorescent probes entrapped in the polymeric micelle core showed that cellular uptake of hydrophobic probes was much faster than that of labeled copolymers. This result implies that the hydrophobic probes in the core are released from micelles in the extracellular space. Forster resonance energy transfer (FRET) imaging and spectroscopy were used to monitor this process ...


Outperforming The Conventional Scaling Rules In The Quantum-Capacitance Limit, Joachim Knoch, W Riess, Joerg Appenzeller Apr 2008

Outperforming The Conventional Scaling Rules In The Quantum-Capacitance Limit, Joachim Knoch, W Riess, Joerg Appenzeller

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We present a study on the scaling behavior of field-effect transistors in the quantum-capacitance limit (QCL). It will be shown that a significant performance improvement in terms of the power delay product can be obtained in devices scaled toward the QCL. As a result, nanowires or nanotubes exhibiting a 1-D transport are a premier choice as active channel materials for transistor devices since the QCL can be attained in such systems.


Determination Of The Eigenstates And Wavefunctions Of A Single Gated As Donor, Gabriel P. Lansbergen, R. Rahman, C. J. Wellard, P. E. Rutten, J. Caro, I. Woo, N. Colleart, S. Biersemans, Gerhard Klimeck Feb 2008

Determination Of The Eigenstates And Wavefunctions Of A Single Gated As Donor, Gabriel P. Lansbergen, R. Rahman, C. J. Wellard, P. E. Rutten, J. Caro, I. Woo, N. Colleart, S. Biersemans, Gerhard Klimeck

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Current semiconductor devices have been scaled to such dimensions that we need take atomistic approach to understand their operation for nano-electronics. From a bottomsup perspective, the smallest functional element within a nanodevice would be a single (dopant) atom itself. Control and understanding over the eigenenergies and wavefunctions of a single dopant could prove a key ingredient for device technology beyond-CMOS. Here, we will discuss the eigenlevels of a single As donor in a three terminal configuration. The donor is incorporated in the channel of prototype transistors called FinFETs. The measured eigenlevels are shown to consist of levels associated with the ...


Externally Assembled Gate-All-Around Carbon Nanotube Field-Effect Transistor, Zhihong Chen, Damon Farmer, Sheng Xu, Roy Gordon, Phaedon Avouris, Joerg Appenzeller Feb 2008

Externally Assembled Gate-All-Around Carbon Nanotube Field-Effect Transistor, Zhihong Chen, Damon Farmer, Sheng Xu, Roy Gordon, Phaedon Avouris, Joerg Appenzeller

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In this letter, we demonstrate a gate-all-around single-wall carbon nanotube field-effect transistor. This is the first successful experimental implementation of an off-chip gate and gate-dielectric assembly with subsequent deposition on a suitable substrate. The fabrication process and device measurements are discussed in the letter. We also argue in how far charges in the gate oxide are responsible for the observed nonideal device performance.


Carbon Nanotubes For High-Performance Electronics - Progress And Prospect, Joerg Appenzeller Feb 2008

Carbon Nanotubes For High-Performance Electronics - Progress And Prospect, Joerg Appenzeller

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Carbon nanotube devices offer intrinsic advantages for high-performance logic device applications. The ultrasmall body of a carbon nanotube-the tube diameter-is the key feature that should allow aggressive channel length scaling, while the intrinsic transport properties of the nanotube ensure at the same time high on-currents. in addition, the narrowness of the tube is critical to implementation of novel device concepts like the tunneling transistor. By understanding the unique capabilities of carbon nanotubes and using them in unconventional designs, novel nanoelectronic applications may become feasible. However, much better control of materials quality must be obtained, and new fabrication processes must be ...


Influence Of Phonon Scattering On The Performance Of P-I-N Band-To-Band Tunneling Transistors, Siyuranga O. Koswatta, Mark S. Lundstrom, Dmitri E. Nikonov Jan 2008

Influence Of Phonon Scattering On The Performance Of P-I-N Band-To-Band Tunneling Transistors, Siyuranga O. Koswatta, Mark S. Lundstrom, Dmitri E. Nikonov

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Power dissipation has become a major obstacle in performance scaling of modern integrated circuits and has spurred the search for devices operating at lower voltage swing. In this letter, we study p-i-n band-to-band tunneling field effect transistors taking semiconducting carbon nanotubes as the channel material. The on current of these devices is mainly limited by the tunneling barrier properties, and phonon-scattering has only a moderate effect. We show, however, that the off current is limited by phonon absorption assisted tunneling, and thus is strongly temperature dependent. Subthreshold swings below the 60 mV/decade conventional limit can be readily achieved even ...


Gold Nanorods Mediate Tumor Cell Death By Compromising Membrane Integrity, Ling Tong, Yan Zhao, Terry B. Huff, Matthew N. Hansen, Alexander Wei, Ji-Xin Cheng Oct 2007

Gold Nanorods Mediate Tumor Cell Death By Compromising Membrane Integrity, Ling Tong, Yan Zhao, Terry B. Huff, Matthew N. Hansen, Alexander Wei, Ji-Xin Cheng

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Folate-conjugated gold nanorods targeted to tumor cell surfaces produced severe membrane damage upon near-infrared irradiation. Photoinduced injury to the plasma membrane resulted in a rapid increase in intracellular calcium (shown in green) with subsequent disruption of the actin network, featured prominently by the formation of membrane blebs.


In Vivo Quantitation Of Rare Circulating Tumor Cells By Multiphoton Intravital Flow Cytometry, Wei He, Haifeng Wang, Lynn C. Hartmann, Ji-Xin Cheng, Phillip S. Low Jul 2007

In Vivo Quantitation Of Rare Circulating Tumor Cells By Multiphoton Intravital Flow Cytometry, Wei He, Haifeng Wang, Lynn C. Hartmann, Ji-Xin Cheng, Phillip S. Low

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Quantitation of circulating tumor cells (CTCs) constitutes an emerging tool for the diagnosis and staging of cancer, assessment of response to therapy, and evaluation of residual disease after surgery. Unfortunately, no existing technology has the sensitivity to measure the low numbers of tumor cells (< 1 CTC per ml of whole blood) that characterize minimal levels of disease. We present a method, intravital flow cytometry, that noninvasively counts rare CTCs in vivo as they flow through the peripheral vasculature. The method involves i.v. injection of a tumor-specific fluorescent ligand followed by multiphoton fluorescence imaging of superficial blood vessels to quantitate the flowing CTCs. Studies in mice with metastatic tumors demonstrate that CTCs can be quantitated weeks before metastatic disease is detected by other means. Analysis of whole blood samples from cancer patients further establishes that human CTCs can be selectively labeled and quantitated when present at approximate to 2 CTCs per ml, opening opportunities for earlier assessment of metastatic disease.


Physics Of Ultrathin-Body Silicon-On-Insulator Schottky-Barrier Field-Effect Transistors, Joachim Knoch, M Zhang, Joerg Appenzeller, S Mantl Jun 2007

Physics Of Ultrathin-Body Silicon-On-Insulator Schottky-Barrier Field-Effect Transistors, Joachim Knoch, M Zhang, Joerg Appenzeller, S Mantl

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In this article we give an overview over the physical mechanisms involved in the electronic transport in ultrathin-body SOI Schottky-barrier MOSFETs. A strong impact of the SOI and gate oxide thickness on the transistor characteristics is found and explained using experimental as well as simulated data. We elaborate on the influence of scattering in the channel and show that for a significant barrier the on-state current is insensitive to scattering once the mean free path for scattering is larger than a characteristic length scale. In addition, recent efforts to lower the Schottky barrier at the source/drain channel interfaces are ...


Understanding Coulomb Effects In Nanoscale Schottky-Barrier-Fets, Klaus M. Indlekofer, Joachim Knoch, Joerg Appenzeller Jun 2007

Understanding Coulomb Effects In Nanoscale Schottky-Barrier-Fets, Klaus M. Indlekofer, Joachim Knoch, Joerg Appenzeller

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We employ a novel multiconfigurational self-consistent Green's function approach (MCSCG) for the simulation of nanoscale Schottky-barrier-field-effect transistors (SB-FETs). This approach allows the calculation of electronic transport with a seamless transition from the single-electron regime to room-temperature FET operation. The particular improvement of the MCSCG stems from a self-consistent division of the channel system into a small subsystem of resonantly trapped states for which a many-body Fock space approach becomes numerically feasible and the rest of the system which can be treated adequately on a conventional mean-field level. The Fock space description allows for the calculation of few-electron Coulomb charging ...


1/F Noise In Carbon Nanotube Devices - On The Impact Of Contacts And Device Geometry, Joerg Appenzeller, Yu-Ming Lin, Joachim Knoch, Zhihong Chen, Phaedon Avouris May 2007

1/F Noise In Carbon Nanotube Devices - On The Impact Of Contacts And Device Geometry, Joerg Appenzeller, Yu-Ming Lin, Joachim Knoch, Zhihong Chen, Phaedon Avouris

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We report on the 1/f noise in various ballistic carbon nanotube devices. A common means to characterize the quality of a transistor in terms of noise is to evaluate the ratio of the noise amplitude A and the sample resistance R. By contacting semiconducting tubes with different metal electrodes we are able to show that a small A/R value by itself is no indication of a suitable metal/tube combination for logic applications. We discuss how current in a nanotube transistor is determined by the injection of carriers at the electrode/nanotube interface, while at the same time ...


Improved Carrier Injection In Ultrathin-Body Soi Schottky-Barrier Mosfets, M Zhang, Joachim Knoch, Joerg Appenzeller, S Mantl Mar 2007

Improved Carrier Injection In Ultrathin-Body Soi Schottky-Barrier Mosfets, M Zhang, Joachim Knoch, Joerg Appenzeller, S Mantl

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The impact of the gate oxide and the silicon-on-insulator (SOI) body thickness on the electrical performance of SOI Schottky-barrier (SB) MOSFETs with fully nickel silicided source and drain contacts is experimentally investigated. The subthreshold swing S is extracted from the experimental data and serves as a measure for the carrier injection through the Sills. It is shown that decreasing the gate oxide and body thickness allows to strongly increase the carrier injection and hence, a significantly improved ON-state of SB-MOSFETs can be obtained.


Hyperthermic Effects Of Gold Nanorods On Tumor Cells, Terry B. Huff, Ling Tong, Matthew N. Hansen, Ji-Xin Cheng, Alexander Wei Feb 2007

Hyperthermic Effects Of Gold Nanorods On Tumor Cells, Terry B. Huff, Ling Tong, Matthew N. Hansen, Ji-Xin Cheng, Alexander Wei

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Plasmon-resonant gold nanorods, which have large absorption cross sections at near-infrared frequencies, are excellent candidates as multifunctional agents for image-guided therapies based on localized hyperthermia. The controlled modification of the surface chemistry of the nanorods is of critical importance, as issues of cell-specific targeting and nonspecific uptake must be addressed prior to clinical evaluation. Nanorods coated with cetyltrimethylammonium bromide (a cationic surfactant used in nanorod synthesis) are internalized within hours into KB cells by a nonspecific uptake pathway, whereas the careful removal of cetyltrimethylammonium bromide from nanorods functionalized with folate results in their accumulation on the cell surface over the ...


Investigation Of Device Parameters For Field-Effect Dna-Sensors By Three-Dimensional Simulation, Eddie Howell, Clemens Heitzinger, Gerhard Klimeck Oct 2006

Investigation Of Device Parameters For Field-Effect Dna-Sensors By Three-Dimensional Simulation, Eddie Howell, Clemens Heitzinger, Gerhard Klimeck

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The development of a DNA field-effect transistor (DNAFET) simulator is described and implications on device structure and future experiments are discussed. In DNAFETs the gate structure is replaced by a layer of immobilized single-stranded DNA molecules which act as surface probe molecules [1, 2]. When complementary DNA strands bind to the receptors, the charge distribution near the surface of the device changes, modulating current transport through the device and enabling detection (cf. Fig. 1 and 5). Arrays of DNAFETs can be used for detecting singlenucleotide polymorphisms and for DNA sequencing. The advantage of DNAFETs over optical methods of detection is ...


Ballisticity Of Nanotube Field-Effect Transistors: Role Of Phonon Energy And Gate Bias, Siyuranga O. Koswatta, Sayed Hasan, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov Jul 2006

Ballisticity Of Nanotube Field-Effect Transistors: Role Of Phonon Energy And Gate Bias, Siyuranga O. Koswatta, Sayed Hasan, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov

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We investigate the role of electron-phonon scattering and gate bias in degrading the drive current of nanotube field-effect transistors (FETs). Optical phonon scattering significantly decreases the drive current only when gate voltage is higher than a well-defined threshold. For comparable electron-phonon coupling, a lower phonon energy leads to a larger degradation of drive current. Thus in semiconductor nanowire FETs, the drive current will be more sensitive than in carbon nanotube FETs because of the smaller phonon energies in semiconductors. Acoustic phonons and other elastic scattering mechanisms are most detrimental to nanotube FETs irrespective of biasing conditions.


Simulation Of Phonon-Assisted Band-To Band Tunneling In Carbon Nanotube Field-Effect Transistors, Siyuranga O. Koswatta, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov Dec 2005

Simulation Of Phonon-Assisted Band-To Band Tunneling In Carbon Nanotube Field-Effect Transistors, Siyuranga O. Koswatta, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov

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Electronic transport in a carbon nanotube metal-oxide-semiconductor field effect transistor (MOSFET) is simulated using the nonequilibrium Green’s functions method with the account of electron-phonon scattering. For MOSFETs, ambipolar conduction is explained via phonon-assisted band-to-band (Landau–Zener) tunneling. In comparison to the ballistic case, we show that the phonon scattering shifts the onset of ambipolar conduction to more positive gate voltage (thereby increasing the off current). It is found that the subthreshold swing in ambipolar conduction can be made as steep as 40 mV/decade despite the effect of phonon scattering.