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2013

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Birck and NCN Publications

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Full-Text Articles in Nanoscience and Nanotechnology

Optical Properties Of Gallium-Doped Zinc Oxide-A Low-Loss Plasmonic Material: First-Principles Theory And Experiment, Jongbum Kim, Gururaj V. Naik, Alexander V. Gavrilenko, Krishnaveni Dondapati, Vladimir I. Gavrilenko, S. M. Prokes, O. J. Glembocki, V. M. Shalaev, Alexandra Boltasseva Dec 2013

Optical Properties Of Gallium-Doped Zinc Oxide-A Low-Loss Plasmonic Material: First-Principles Theory And Experiment, Jongbum Kim, Gururaj V. Naik, Alexander V. Gavrilenko, Krishnaveni Dondapati, Vladimir I. Gavrilenko, S. M. Prokes, O. J. Glembocki, V. M. Shalaev, Alexandra Boltasseva

Birck and NCN Publications

Searching for better materials for plasmonic and metamaterial applications is an inverse design problem where theoretical studies are necessary. Using basic models of impurity doping in semiconductors, transparent conducting oxides (TCOs) are identified as low-loss plasmonic materials in the near-infrared wavelength range. A more sophisticated theoretical study would help not only to improve the properties of TCOs but also to design further lower-loss materials. In this study, optical functions of one such TCO, gallium-doped zinc oxide (GZO), are studied both experimentally and by first-principles density-functional calculations. Pulsed-laser-deposited GZO films are studied by the x-ray diffraction and generalized spectroscopic ellipsometry. Theoretical …

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Spatial Spectrograms Of Vibrating Atomic Force Microscopy Cantilevers Coupled To Sample Surfaces, Ryan Wagner, Arvind Raman, Roger Proksch Dec 2013

Spatial Spectrograms Of Vibrating Atomic Force Microscopy Cantilevers Coupled To Sample Surfaces, Ryan Wagner, Arvind Raman, Roger Proksch

Birck and NCN Publications

Many advanced dynamic Atomic Force Microscopy (AFM) techniques such as contact resonance, force modulation, piezoresponse force microscopy, electrochemical strain microscopy, and AFM infrared spectroscopy exploit the dynamic response of a cantilever in contact with a sample to extract local material properties. Achieving quantitative results in these techniques usually requires the assumption of a certain shape of cantilever vibration. We present a technique that allows in-situ measurements of the vibrational shape of AFM cantilevers coupled to surfaces. This technique opens up unique approaches to nanoscale material property mapping, which are not possible with single point measurements alone. (C) 2013 AIP Publishing …

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The Role Of Oxygen In The Uptake Of Deuterium In Lithiated Graphite, C. N. Taylor, J. Dadras, Kara E. Luitjohan, Jean P. Allain, P. S. Kristic, C. H. Skinner Dec 2013

The Role Of Oxygen In The Uptake Of Deuterium In Lithiated Graphite, C. N. Taylor, J. Dadras, Kara E. Luitjohan, Jean P. Allain, P. S. Kristic, C. H. Skinner

Birck and NCN Publications

We investigate the mechanism of deuterium retention by lithiated graphite and its relationship to the oxygen concentration through surface sensitive experiments and atomistic simulations. Deposition of lithium on graphite yielded 5%-8% oxygen surface concentration and when subsequently irradiated with D ions at energies between 500 and 1000 eV/amu and fluences over 10(16) cm(-2) the oxygen concentration rose to between 25% and 40%. These enhanced oxygen levels were reached in a few seconds compared to about 300 h when the lithiated graphite was allowed to adsorb oxygen from the ambient environment under equilibrium conditions. Irradiating graphite without lithium deposition, however, resulted …

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Limit For Thermal Transport Reduction In Si Nanowires With Nanoengineered Corrugations, Sean E. Sullivan, Keng-Hua Lin, Stanislav Avdoshenko, Alejandro Strachan Dec 2013

Limit For Thermal Transport Reduction In Si Nanowires With Nanoengineered Corrugations, Sean E. Sullivan, Keng-Hua Lin, Stanislav Avdoshenko, Alejandro Strachan

Birck and NCN Publications

Non-equilibrium molecular dynamics simulations reveal that the thermal conductance of Si nanowires with periodic corrugations is lower than that of smooth wires with cross-sections equivalent to the constricted portions. This reduction in conductance is up to 30% and tends to plateau with increasing corrugation height. Spatially resolved temperature and heat current maps provide a microscopic understanding of this effect; we find that 80% of the heat current is carried through the constricted area even for high-amplitude corrugations. More importantly, we show that temperature gradient inversion and heat current vortices at the ridge peaks establish fundamental limits on maximum conductance reduction. …

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Homogeneous Algan/Gan Superlattices Grown On Free-Standing (1(1)Over-Bar00) Gan Substrates By Plasma-Assisted Molecular Beam Epitaxy, Jiayi Shao, Dmitri N. Zakharov, Collin Edmunds, Oana Malis, Michael J. Manfra Dec 2013

Homogeneous Algan/Gan Superlattices Grown On Free-Standing (1(1)Over-Bar00) Gan Substrates By Plasma-Assisted Molecular Beam Epitaxy, Jiayi Shao, Dmitri N. Zakharov, Collin Edmunds, Oana Malis, Michael J. Manfra

Birck and NCN Publications

Two-dimensional and homogeneous growth of m-plane AlGaN by plasma-assisted molecular beam epitaxy has been realized on free-standing (1 (1) over bar 00) GaN substrates by implementing high metal-to-nitrogen (III/N) flux ratio. AlN island nucleation, often reported for m-plane AlGaN under nitrogen-rich growth conditions, is suppressed at high III/N flux ratio, highlighting the important role of growth kinetics for adatom incorporation. The homogeneity and microstructure of m-plane AlGaN/GaN superlattices are assessed via a combination of scanning transmission electron microscopy and high resolution transmission electron microscopy (TEM). The predominant defects identified in dark field TEM characterization are short basal plane stacking faults …

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Near Sputter-Threshold Gasb Nanopatterning, Osman El-Atwani, Sean Gonderman, Jean Paul Allain Sep 2013

Near Sputter-Threshold Gasb Nanopatterning, Osman El-Atwani, Sean Gonderman, Jean Paul Allain

Birck and NCN Publications

Nanopatterning at sputter-threshold energies with Ar irradiation of GaSb (100) surfaces is presented. Comparison with high-energy irradiations up to 1000 eV is conducted measuring in-situ the composition evolution over irradiation time at early stages (e. g., < 10(17) cm(-2)) and up to nanostructure saturation (e. g., similar to 10(18) cm(-2)). Low-energy irradiation is conducted for energies between 15-100 eV and a low-aspect ratio nanostructured dot formation is found. Furthermore, the role of oxide on GaSb is found to delay nanostructure formation and this is predominant at energies below 100 eV. In-situ quartz crystal microbalance measurements collect sputtered particles yielding the sputter rate at threshold energies indicating a correlation between erosion and surface composition consistent with recent theoretical models. Ion-induced segregation is also found and indicated by both compositional measurements of both the surface and the sputtered plume. (C) 2013 AIP Publishing LLC.

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Giant Quasiparticle Bandgap Modulation In Graphene Nanoribbons Supported On Weakly Interacting Surfaces, Xueping Jiang, Neerav Kharche, Paul Kohl, Timothy B. Boykin, Gerhard Klimeck, Mathieu Luisier, Pulickel M. Ajayan, Saroj K. Nayak Sep 2013

Giant Quasiparticle Bandgap Modulation In Graphene Nanoribbons Supported On Weakly Interacting Surfaces, Xueping Jiang, Neerav Kharche, Paul Kohl, Timothy B. Boykin, Gerhard Klimeck, Mathieu Luisier, Pulickel M. Ajayan, Saroj K. Nayak

Birck and NCN Publications

In general, there are two major factors affecting bandgaps in nanostructures: (i) the enhanced electron-electron interactions due to confinement and (ii) the modified selfenergy of electrons due to the dielectric screening. While recent theoretical studies on graphene nanoribbons (GNRs) report on the first effect, the effect of dielectric screening from the surrounding materials such as substrates has not been thoroughly investigated. Using large-scale electronic structure calculations based on the GW approach, we show that when GNRs are deposited on substrates, bandgaps get strongly suppressed (by as much as 1 eV) even though the GNR-substrate interaction is weak.

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Quantum Hall Effect In Monolayer-Bilayer Graphene Planar Junctions, Jifa Tian, Yongjin Jiang, Isaac Childres, Helin Cao, Jiangping Hu, Yong P. Chen Sep 2013

Quantum Hall Effect In Monolayer-Bilayer Graphene Planar Junctions, Jifa Tian, Yongjin Jiang, Isaac Childres, Helin Cao, Jiangping Hu, Yong P. Chen

Birck and NCN Publications

The Hall resistance of a homogeneous electron system is well known to be antisymmetric with respect to the magnetic field and the sign of charge carriers. We have observed that such symmetries no longer hold in planar hybrid structures consisting of partly single layer graphene (SLG) and partly bilayer graphene (BLG) in the quantum Hall (QH) regime. In particular, the Hall resistance across the SLG and BLG interface is observed to exhibit quantized plateaus that switch between those characteristic of SLG QH states and BLG QH states when either the sign of the charge carriers (controlled by a back gate) …

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Effects Of Nanocrystal Shape And Size On The Temperature Sensitivity In Raman Thermometry, Liangliang Chen, Kelly Rickey, Qing Zhao, Christopher Robinson, Xiulin Ruan Aug 2013

Effects Of Nanocrystal Shape And Size On The Temperature Sensitivity In Raman Thermometry, Liangliang Chen, Kelly Rickey, Qing Zhao, Christopher Robinson, Xiulin Ruan

Birck and NCN Publications

The effects of CdSe nanocrystal (NC) shape and size on the temperature sensitivity of the Raman shift have been investigated, for the interest of Raman thermometry using NCs. For spherical CdSe NCs of diameters 2.8 nm, 3.6 nm, and 4.4 nm, the temperature sensitivities are -0.0131 cm(-1)/K, -0.0171 cm(-1)/K, and -0.0242 cm(-1)/K, respectively. This trend indicates that as the diameter increases, the effect of increasing phonon anharmonicity dominates over the effect of the decreasing thermal expansion coefficient. On the other hand, triangular NCs with a size of 4.2 nm and elongated NCs of a dimension of 4.6 nm by 14 …

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Electronic And Optical Properties Of Scn And (Sc,Mn)N Thin Films Deposited By Reactive Dc-Magnetron Sputtering, Bivas Saha, Gururaj V. Naik, Vladimir P. Drachev, Alexandra Boltasseva, Ernesto Marinero, Timothy D. Sands Aug 2013

Electronic And Optical Properties Of Scn And (Sc,Mn)N Thin Films Deposited By Reactive Dc-Magnetron Sputtering, Bivas Saha, Gururaj V. Naik, Vladimir P. Drachev, Alexandra Boltasseva, Ernesto Marinero, Timothy D. Sands

Birck and NCN Publications

Scandium nitride (ScN) is a rocksalt semiconductor that has attracted significant attention from various researchers for a diverse range of applications. Motivated by the prospect of using its interesting electronic structure for optoelectronic and dilute magnetic semiconductor applications, we present detailed studies of the electronic transport and optical properties of ScN and its alloys with manganese nitride (MnN). Our results suggest (a) dilute manganese doping in ScN compensates for the high n-type carrier concentrations arising due to oxygen impurities and (b) an n-type to p-type carrier type transition occurs at a composition between 5.8% and 11% Mn on Sc sites. …

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Frequency Response Of Atmospheric Pressure Gas Breakdown In Micro/Nanogaps, Abbas Semnani, Ayyaswamy Venkattraman, Alina A. Alexeenko, Dimitrios Peroulis Aug 2013

Frequency Response Of Atmospheric Pressure Gas Breakdown In Micro/Nanogaps, Abbas Semnani, Ayyaswamy Venkattraman, Alina A. Alexeenko, Dimitrios Peroulis

Birck and NCN Publications

In this paper, we study gas breakdown in micro/nanogaps at atmospheric pressure from low RF to high millimeter band. For gaps larger than about 10 mu m, the breakdown voltage agrees with macroscale vacuum experiments, exhibiting a sharp decrease at a critical frequency, due to transition between the boundary- and diffusion-controlled regimes, and a gradual increase at very high frequencies as a result of inefficient energy transfer by field. For sub-micron gaps, a much lower breakdown is obtained almost independent of frequency because of the dominance of field emission. (C) 2013 AIP Publishing LLC.

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A Humidity-Sensitive Hydrogel-Bacillus Spore Composite For Micropatterning Of Biomolecular Gradients, Richard L. Gieseck, Bin-Da Chan, Cagri A. Savran Aug 2013

A Humidity-Sensitive Hydrogel-Bacillus Spore Composite For Micropatterning Of Biomolecular Gradients, Richard L. Gieseck, Bin-Da Chan, Cagri A. Savran

Birck and NCN Publications

A composite material consisting of Bacillus subtilis spores suspended in a humidity sensitive hydrogel can be used to pattern biomolecules in different concentrations directly onto glass surfaces using a mechanical micromanipulator. By altering the relative humidity surrounding the composite gel during deposition, surface concentration of patterned biomolecules can be controlled and varied to create user-defined, biomolecular surface concentrations. (C) 2013 AIP Publishing LLC.

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Mapping The 3d Surface Potential In Bi2se3, Chris Mann, Damien West, Ireneusz Miotkowski, Yong P. Chen, Shengbai Zhang, Chih-Kang Shih Aug 2013

Mapping The 3d Surface Potential In Bi2se3, Chris Mann, Damien West, Ireneusz Miotkowski, Yong P. Chen, Shengbai Zhang, Chih-Kang Shih

Birck and NCN Publications

Bi2Se3 initially emerged as a particularly promising host of topological physics. However, in actual materials, several issues have been uncovered including strong surface band bending and potential fluctuations. To investigate these concerns, we study nominally stoichiometric Bi2Se3 using scanning tunnelling microscopy. Here we identify two distinct distributions of Bi-Se antisites that act as nanometer-scale sensors for the surface band-bending field. To confirm this, we examine bulk Cu-doped Bi2Se3 and demonstrate a significantly reduced surface band-bending field. In addition, we find that in the case of unintentionally doped Bi2Se3, lateral fluctuations of the Dirac point can be directly correlated with specific …

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Hysteretic Response Of Chemical Vapor Deposition Graphene Field Effect Transistors On Sic Substrates, Edward Cazalas, Isaac Childres, Amanda Majcher, Ting Fung Chung, Yong P. Chen, Igor Jovanovic Jul 2013

Hysteretic Response Of Chemical Vapor Deposition Graphene Field Effect Transistors On Sic Substrates, Edward Cazalas, Isaac Childres, Amanda Majcher, Ting Fung Chung, Yong P. Chen, Igor Jovanovic

Birck and NCN Publications

Graphene field effect transistors (GFETs) fabricated by chemical vapor deposition graphene deposited onto SiC substrates exhibit sensitivity to broadband visible light. The hysteretic nature of this GFET type was studied utilizing a new current-voltage measurement technique in conjunction with current-time measurements. This measurement method accounts for hysteretic changes in graphene response and enables transfer measurements that can be attributed to fixed gate voltages. Graphene hysteresis is shown to be consistent with electrochemical p-type doping, and current-time measurements clearly resolve a hole to electron to hole carrier transition in graphene with a single large change in gate voltage. (C) 2013 AIP …

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Surface Morphology Evolution Of M-Plane (1(1)Over-Bar00) Gan During Molecular Beam Epitaxy Growth: Impact Of Ga/N Ratio, Miscut Direction, And Growth Temperature, Jiayi Shao, Liang Tang, Colin Edmunds, Geoff C. Gardner, Oana Malis, Michael J. Manfra Jul 2013

Surface Morphology Evolution Of M-Plane (1(1)Over-Bar00) Gan During Molecular Beam Epitaxy Growth: Impact Of Ga/N Ratio, Miscut Direction, And Growth Temperature, Jiayi Shao, Liang Tang, Colin Edmunds, Geoff C. Gardner, Oana Malis, Michael J. Manfra

Birck and NCN Publications

We present a systematic study of morphology evolution of [1 (1) over bar 00] m-plane GaN grown by plasma-assisted molecular beam epitaxy on free-standing m-plane substrates with small miscut angles towards the -c [000 (1) over bar] and +c [0001] directions under various gallium to nitrogen (Ga/N) ratios at substrate temperatures T = 720 degrees C and T = 740 degrees C. The miscut direction, Ga/N ratio, and growth temperature are all shown to have a dramatic impact on morphology. The observed dependence on miscut direction supports the notion of strong anisotropy in the gallium adatom diffusion barrier and growth …

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Silicon Quantum Electronics, Floris A. Zwanenburg, Andrew S. Dzurak, Andrea Morello, Michelle Y. Simmons, Lloyd C. L. Hollenberg, Gerhard Klimeck, Sven Rogge, Susan N. Coppersmith, Mark A. Eriksson Jul 2013

Silicon Quantum Electronics, Floris A. Zwanenburg, Andrew S. Dzurak, Andrea Morello, Michelle Y. Simmons, Lloyd C. L. Hollenberg, Gerhard Klimeck, Sven Rogge, Susan N. Coppersmith, Mark A. Eriksson

Birck and NCN Publications

This review describes recent groundbreaking results in Si, Si/SiGe, and dopant-based quantum dots, and it highlights the remarkable advances in Si-based quantum physics that have occurred in the past few years. This progress has been possible thanks to materials development of Si quantum devices, and the physical understanding of quantum effects in silicon. Recent critical steps include the isolation of single electrons, the observation of spin blockade, and single-shot readout of individual electron spins in both dopants and gated quantum dots in Si. Each of these results has come with physics that was not anticipated from previous work in other …

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Quest For Organic Plasmonics, Lei Gu, J. Livenere, G. Zhu, Evgenii E. Narimanov, M. A. Noginov Jul 2013

Quest For Organic Plasmonics, Lei Gu, J. Livenere, G. Zhu, Evgenii E. Narimanov, M. A. Noginov

Birck and NCN Publications

Many photonic metamaterials and plasmonic devices, in spite of their unparalleled responses to light waves and nearly fantastic applications, suffer from absorption loss in constituent metallic components. Unfortunately, none of the known techniques aimed to conquer the absorption loss has led to a revolutionary technological breakthrough, prompting a continuing quest for efficient solutions to the loss problem. In this letter, we study optical properties of non-metallic organic plasmonic and epsilon-near-zero materials and demonstrate propagation of a surface plasmon polariton at the interface between solid organic dye and air. (C) 2013 AIP Publishing LLC.

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High Precision Dynamic Alignment And Gap Control For Optical Near-Field Nanolithography, Xiaolei Wen, Luis M. Traverso, Pornsak Srisungsitthisunti, Xianfan Xu, Euclid E. Moon Jul 2013

High Precision Dynamic Alignment And Gap Control For Optical Near-Field Nanolithography, Xiaolei Wen, Luis M. Traverso, Pornsak Srisungsitthisunti, Xianfan Xu, Euclid E. Moon

Birck and NCN Publications

The authors demonstrate the use of interferometric-spatial-phase-imaging (ISPI) to control a gap distance of the order of nanometers for parallel optical near-field nanolithography. In optical near-field nanolithography, the distance between the optical mask and the substrate needs to be controlled within tens of nanometers or less. The ISPI technique creates interference fringes from checkerboard gratings fabricated on the optical mask, which are used to determine the gap distance between the mask and the substrate surfaces. The sensitive of this gapping technique can reach 0.15 nm. With the use of ISPI and a dynamic feedback control system, the authors can precisely …

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Growth And Electrical Characterization Of Al0.24ga0.76as/Alxga1-Xas/Al0.24ga0.76as Modulation-Doped Quantum Wells With Extremely Low X, Geoff C. Gardner, John D. Watson, Sumit Mondal, Nianpei Deng, Gabor A. Csathy, Michael J. Manfra Jun 2013

Growth And Electrical Characterization Of Al0.24ga0.76as/Alxga1-Xas/Al0.24ga0.76as Modulation-Doped Quantum Wells With Extremely Low X, Geoff C. Gardner, John D. Watson, Sumit Mondal, Nianpei Deng, Gabor A. Csathy, Michael J. Manfra

Birck and NCN Publications

We report on the growth and electrical characterization of modulation-doped Al0.24Ga0.76As/AlxGa1-xAs/Al0.24Ga0.76As quantum wells with mole fractions as low as x = 0.00057. Such structures will permit detailed studies of the impact of alloy disorder in the fractional quantum Hall regime. At zero magnetic field, we extract an alloy scattering rate of 24 ns(-1) per% Al. Additionally, we find that for x as low as 0.00057 in the quantum well, alloy scattering becomes the dominant mobility-limiting scattering mechanism in ultra-high purity two-dimensional electron gases typically used to study the fragile nu = 5/2 and nu = 12/5 fractional quantum Hall states. …

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Investigation Of Ripple-Limited Low-Field Mobility In Large-Scale Graphene Nanoribbons, M. Luisier, T. B. Boykin, Z. Ye, A. Martini, Gerhard Klimeck, N. Kharche, X. Jiang, S. Nayak Jun 2013

Investigation Of Ripple-Limited Low-Field Mobility In Large-Scale Graphene Nanoribbons, M. Luisier, T. B. Boykin, Z. Ye, A. Martini, Gerhard Klimeck, N. Kharche, X. Jiang, S. Nayak

Birck and NCN Publications

Combining molecular dynamics and quantum transport simulations, we study the degradation of mobility in graphene nanoribbons caused by substrate-induced ripples. First, the atom coordinates of large-scale structures are relaxed such that surface properties are consistent with those of graphene on a substrate. Then, the electron current and low-field mobility of the resulting non-flat nanoribbons are calculated within the Non-equilibrium Green's Function formalism in the coherent transport limit. An accurate tight-binding basis coupling the sigma- and pi-bands of graphene is used for this purpose. It is found that the presence of ripples decreases the mobility of graphene nanoribbons on SiO2 below …

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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

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

Birck and NCN Publications

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

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