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Full-Text Articles in Nanoscience and Nanotechnology

Boron Carbide/N-Silicon Carbide Heterojunction Diodes, Shireen Adenwalla, P. Welsch, A. Harken, Jennifer I. Brand, A. Sezer, Brian W. Robertson Dec 2001

Boron Carbide/N-Silicon Carbide Heterojunction Diodes, Shireen Adenwalla, P. Welsch, A. Harken, Jennifer I. Brand, A. Sezer, Brian W. Robertson

Faculty Publications from Nebraska Center for Materials and Nanoscience

The fabrication, initial structural characterization, and diode measurements are reported for a boron carbide/silicon carbide heterojunction diode. Current–voltage curves are obtained for operation at temperatures from 24 to 351 °C. Plasma-enhanced chemical-vapor deposition (PECVD) -deposited undoped boron carbide material is highly crystalline and consists of a variety of polytypes of boron carbide (BC) with crystal sizes as large as 110 nm. Crystal phases are similar to those for PECVD BC on Si but only partially match known boron and boron-rich BC phases.


Anisotropy Of Conducting P States And 11B Nuclear Spin-Lattice Relaxation In Mg1-XAlXB2, Kirill D. Belashchenko, Vladimir B. Antropov, S.N. Rashkeev Aug 2001

Anisotropy Of Conducting P States And 11B Nuclear Spin-Lattice Relaxation In Mg1-XAlXB2, Kirill D. Belashchenko, Vladimir B. Antropov, S.N. Rashkeev

Faculty Publications from Nebraska Center for Materials and Nanoscience

We calculated the nuclear spin-lattice relaxation rate in the Mg1-xAlxB2 system and found that the orbital relaxation mechanism dominates over the dipolar and Fermi-contact mechanisms in MgB2, whereas in AlB2 due to a smaller density of states and strong anisotropy of boron p orbitals the relaxation is completely determined by Fermi-contact interaction. The results for MgB2 are compared with existing experimental data. To validate the theory, nuclear resonance experiments for the studied diboride alloy system are needed.


Coexistence Of Covalent And Metallic Bonding In The Boron Intercalation Superconductor Mgb2, Kirill D. Belashchenko, Mark Van Schilfgaarde, Vladimir P. Antropov Aug 2001

Coexistence Of Covalent And Metallic Bonding In The Boron Intercalation Superconductor Mgb2, Kirill D. Belashchenko, Mark Van Schilfgaarde, Vladimir P. Antropov

Faculty Publications from Nebraska Center for Materials and Nanoscience

Chemical bonding and electronic structure of MgB2, a boron-based newly discovered superconductor, is studied using self-consistent band-structure techniques. Analysis of the transformation of the band structure for the hypothetical series of graphite–primitive graphite–primitive graphitelike boron–intercalated boron, shows that the band structure of MgB2 is graphitelike, with π bands falling deeper than in ordinary graphite. These bands possess a typically delocalized and metallic, as opposed to covalent, character. The in-plane σ bands retain their two-dimensional (2D) covalent character, but exhibit a metallic hole-type conductivity. The coexistence of 2D covalent in-plane and three-dimensional (3D) metallic-type interlayer conducting ...


Superconductivity Of Metallic Boron In Mgb2, J. Kortus, I.I. Mazin, Kirill D. Belashchenko, Vladimir P. Antropov, L.L. Boyer May 2001

Superconductivity Of Metallic Boron In Mgb2, J. Kortus, I.I. Mazin, Kirill D. Belashchenko, Vladimir P. Antropov, L.L. Boyer

Faculty Publications from Nebraska Center for Materials and Nanoscience

Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm-1, this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical ...


Scattering Of Elastic Waves In Heterogeneous Media With Local Isotropy, Joseph A. Turner, Phanidhar Anugonda May 2001

Scattering Of Elastic Waves In Heterogeneous Media With Local Isotropy, Joseph A. Turner, Phanidhar Anugonda

Faculty Publications from Nebraska Center for Materials and Nanoscience

The scattering of elastic waves in heterogeneous media is discussed. Explicit expressions are derived for the attenuation of longitudinal and transverse elastic waves in terms of the statistics of the density and Lame´ parameter fluctuations. The derivation is based upon diagrammatic methods with the problem posed in terms of the Dyson equation. The Dyson equation is solved for the mean field response. The results are given here in a straightforward manner, in which the attenuations reduce to simple integrals on the unit circle. The medium is assumed statistically homogeneous and statistically isotropic. This model, with assumed local isotropic properties, is ...


Bistable Operation Of A Two-Section 1.3-Mm Inas Quantum Dot Laser—Absorption Saturation And The Quantum Confined Stark Effect, Xiaodong Huang, A. Stintz, Hua Li, Audra Rice, G. T. Liu, L.F. Lester, Julian Cheng, K.J. Malloy Mar 2001

Bistable Operation Of A Two-Section 1.3-Mm Inas Quantum Dot Laser—Absorption Saturation And The Quantum Confined Stark Effect, Xiaodong Huang, A. Stintz, Hua Li, Audra Rice, G. T. Liu, L.F. Lester, Julian Cheng, K.J. Malloy

Faculty Publications

Room temperature, continuous-wave bistability was observed in oxide-confined, two-section, 1.3- m quantum-dot (QD) lasers with an integrated intracavity quantum-dot saturable absorber. The origin of the hysteresis and bistability were shown to be due to the nonlinear saturation of the QD absorption and the electroabsorption induced by the quantum confined Stark effect.


Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills (2), João F. Gomes Jan 2001

Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills (2), João F. Gomes

João F Gomes

This paper describes work performed on the sampling and analysis of non-condensable gases (NCG) emitted from diffuse sources of a Portuguese Kraft pulp mill, which is the background information for a NCG collection, treatment and disposal system. The variability found in the composition of the gaseous compounds showed the existence of gaseous streams other than typical total reduced sulphur (TRS) compounds as usually described. From the measured TRS concentrations and the gas flow rate from each source it was possible to calculate the emission flow rate, E, of each source. These emission flow rates were then divided into 3 categories ...


Static Friction And Surface Roughness Studies Of Surface Micromachined Electrostatic Micromotors Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan Jan 2001

Static Friction And Surface Roughness Studies Of Surface Micromachined Electrostatic Micromotors Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan

Sriram Sundararajan

A technique to measure the static friction forces (stiction) encountered in surface micromachined micromotors using a commercial atomic force microscope (AFM)/friction force microscope has been developed and is described. An AFM tip is pushed against a rotor arm of the micromotor so as to generate lateral deflection (torsion) of the tip, which is measured by the AFM. The maximum value of the lateral deflection obtained prior to rotor movement (rotation) is a measure of the static friction force of the micromotors. This technique was employed to study the effect of humidity and rest time on the static friction force ...


Preparation Of Magnetic Nanoparticles And Their Assemblies Using A New Fe(Ii) Alkoxide Precursor, Suresh Pillai, Grainne Biddlecombe, Yurii Gun’Ko, John Kelly, J. Michael Coey, Alexis Douvalis Jan 2001

Preparation Of Magnetic Nanoparticles And Their Assemblies Using A New Fe(Ii) Alkoxide Precursor, Suresh Pillai, Grainne Biddlecombe, Yurii Gun’Ko, John Kelly, J. Michael Coey, Alexis Douvalis

Articles

No abstract provided.


Development Of A Continuous Microscratch Technique In An Atomic Force Microscope And Its Application To Study Scratch Resistance Of Ultrathin Hard Amorphous Carbon Coatings, Sriram Sundararajan, Bharat Bhushan Dec 2000

Development Of A Continuous Microscratch Technique In An Atomic Force Microscope And Its Application To Study Scratch Resistance Of Ultrathin Hard Amorphous Carbon Coatings, Sriram Sundararajan, Bharat Bhushan

Sriram Sundararajan

A method to measure friction during scratching at linearly increasing loads in a commercial atomic force/friction force microscope (AFM/FFM) has been developed. The normal load was increased in small increments over the required range for the scratch using a software module while the friction signal was measured via a breakout box and data acquisition computer. Topography images of the scratch were obtained in situ with the AFM in tapping mode with minimal loss of damage event information. This technique was employed to study the scratch resistance of hard amorphous carbon coatings of thicknesses ranging from 20 nm down ...