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2010

Birck and NCN Publications

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Articles 31 - 38 of 38

Full-Text Articles in Nanoscience and Nanotechnology

Electronic Structure, Phonons, And Thermal Properties Of Scn, Zrn, And Hfn: A First-Principles Study, Bivas Saha, Jagaran Acharya, Timothy D. Sands, Umesh Waghmare Feb 2010

Electronic Structure, Phonons, And Thermal Properties Of Scn, Zrn, And Hfn: A First-Principles Study, Bivas Saha, Jagaran Acharya, Timothy D. Sands, Umesh Waghmare

Birck and NCN Publications

With a motivation to understand microscopic aspects of ScN, ZrN, and HfN relevant to the thermoelectric properties of nitride metal/semiconductor superlattices, we determine their electronic structure, vibrational spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find a large energy gap in the phonon dispersions of metallic ZrN and HfN, but a gapless phonon spectrum for ScN spanning the same energy range, this suggests that a reduced thermal conductivity, suitable for thermoelectric applications, should arise in superlattices made with ScN and ZrN or ScN and HfN. …


Complex Martensitic Nanostructure In Zr Nanowires: A Molecular Dynamics Study, Alexander Thompson, Alejandro Strachan Feb 2010

Complex Martensitic Nanostructure In Zr Nanowires: A Molecular Dynamics Study, Alexander Thompson, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics to characterize the martensitic nanostructure that develops when bcc Zr nanowires are cooled down and transform to hcp (martensite). We find that size has a strong effect on nanostructure and even very small wires (a few nanometers in diameter) exhibit complex, multidomain structures with large internal strains (up to similar to 6%). Long and thin wires result in domains coexisting along their axes while those with small aspect ratios exhibit coexistence of domains within their cross-section. We also that find regions of fcc Zr that develop to bridge neighboring hcp domains.


Scanning Tunneling Microscope Study Of Striated Carbon Ridges In Few-Layer Epitaxial Graphene Formed On 4h-Silicon Carbide (0001), Sara E. Harrison, Michael A. Capano, R. Reifenberger Feb 2010

Scanning Tunneling Microscope Study Of Striated Carbon Ridges In Few-Layer Epitaxial Graphene Formed On 4h-Silicon Carbide (0001), Sara E. Harrison, Michael A. Capano, R. Reifenberger

Birck and NCN Publications

Atomically resolved scanning tunneling microscope images of carbon ridge defects found in few-layer graphene formed on the C-face (0001) of 4H-silicon carbide reveal a striated exterior surface formed from out-of-plane distortions of the hexagonal graphene lattice. While ridge formation is likely explained by compressive in-plane stresses coupled with the small values of the bending modulus for few-layer graphene, the striated structure along the ridges argues for a localized unidirectional stress in the material directed along the ridge length.


Molecular Modulation Of Schottky Barrier Height In Metal-Molecule-Silicon Diodes: Capacitance And Simulation Results, Adina Scott, Chad Risko, Nicholas Valley, Mark A. Ratner, David B. Janes Jan 2010

Molecular Modulation Of Schottky Barrier Height In Metal-Molecule-Silicon Diodes: Capacitance And Simulation Results, Adina Scott, Chad Risko, Nicholas Valley, Mark A. Ratner, David B. Janes

Birck and NCN Publications

There is considerable current interest in using molecular materials to influence the surface potential of semiconductor devices for nanoelectronic and sensing applications. We present experimental capacitance-voltage results showing that systematic Schottky barrier height modulation can be achieved using dipolar molecular layers in gold-molecule-silicon devices. A computational methodology that combines quantum chemistry and traditional electrostatic calculations is used to explore various physical effects that can influence barrier heights in such systems. Nonidealities such as silicon surface states can influence both the potential profile within the device and the validity of the extracted barrier height. Our devices exhibit low surface state densities, …


On Landauer Versus Boltzmann And Full Band Versus Effective Mass Evaluation Of Thermoelectric Transport Coefficients, Changwook Jeong, Raseong Kim, Mathieu Luisier, Supriyo Datta, Mark S. Lundstrom Jan 2010

On Landauer Versus Boltzmann And Full Band Versus Effective Mass Evaluation Of Thermoelectric Transport Coefficients, Changwook Jeong, Raseong Kim, Mathieu Luisier, Supriyo Datta, Mark S. Lundstrom

Birck and NCN Publications

Using a full band description of electronic bandstructure, the Landauer approach to diffusive transport is mathematically related to the solution of the Boltzmann transport equation, and expressions for the thermoelectric parameters in both formalisms are presented. Quantum mechanical and semiclassical techniques to obtain from a full description of the bandstructure, E(k), the density of modes in the Landauer approach or the transport distribution in the Boltzmann solution are compared and thermoelectric transport coefficients are evaluated. Several example calculations for representative bulk materials are presented and the full band results are related to the more common effective mass formalism. Finally, given …


Accurate Force Spectroscopy In Tapping Mode Atomic Force Microscopy In Liquids, Xin Xu, John Melcher, Arvind Raman Jan 2010

Accurate Force Spectroscopy In Tapping Mode Atomic Force Microscopy In Liquids, Xin Xu, John Melcher, Arvind Raman

Birck and NCN Publications

Existing force spectroscopy methods in tapping mode atomic force microscopy (AFM) such as higher harmonic inversion [M. Stark, R. W. Stark, W. M. Heckl, and R. Guckenberger, Proc. Natl. Acad. Sci. U. S. A. 99, 8473 (2002)] or scanning probe acceleration microscopy [J. Legleiter, M. Park, B. Cusick, and T. Kowalewski, Proc. Natl. Acad. Sci. U. S. A. 103, 4813 (2006)] or integral relations [M. Lee and W. Jhe, Phys. Rev. Lett. 97, 036104 (2006); S. Hu and A. Raman, Nanotechnology 19, 375704 (2008); H. Holscher, Appl. Phys. Lett. 89, 123109 (2006); A. J. Katan, Nanotechnology 20, 165703 (2009)] require …


Quantum Approach To Electronic Noise Calculations In The Presence Of Electron-Phonon Interactions, Hong-Hyun Park, Gerhard Klimeck Jan 2010

Quantum Approach To Electronic Noise Calculations In The Presence Of Electron-Phonon Interactions, Hong-Hyun Park, Gerhard Klimeck

Birck and NCN Publications

A quantum-mechanical approach to the calculation of electronic noise for nanoscale devices is presented. This method is based on the nonequilibrium Green’s-function formalism with electron-phonon scattering mechanisms and takes the effects of the Pauli exclusion principle and the long-range Coulomb interactions into account. As examples the drain current noise characteristics of silicon nanowire transistors at room temperature are simulated. The drain current noise in the saturation regime is primarily shot-noise dominant but is suppressed for higher gate biases due to the electron-electron correlation in the channel region. The role of electron-phonon interactions on noise, the transition from thermal to shot …


Theory Of ‘Selectivity’ Of Label-Free Nanobiosensors – A Geometro-Physical Perspective, Pradeep R. Nair, Muhammad A. Alam Jan 2010

Theory Of ‘Selectivity’ Of Label-Free Nanobiosensors – A Geometro-Physical Perspective, Pradeep R. Nair, Muhammad A. Alam

Birck and NCN Publications

Modern label-free biosensors are generally far more sensitive and require orders of magnitude less incubation time compared to their classical counterparts. However, a more important characteristic regarding the viability of this technology for applications in Genomics/Proteomics is defined by the ‘Selectivity’, i.e., the ability to concurrently and uniquely detect multiple target biomolecules in the presence of interfering species. Currently, there is no theory of Selectivity that allows optimization of competing factors and there are few experiments to probe this problem systematically. In this article, we use the elementary considerations of surface exclusion, diffusion limited transport, and void distribution function to …