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Search Publications by: Igor Levin (Fed)

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Displaying 76 - 100 of 132

Subsolidus Phase Equilibria and Properties in the Magnetic Dielectric System Bi 2 O 3 :Mn 2 O 3+x :Nb 2 O 5

July 20, 2006
Author(s)
Terrell A. Vanderah, M W. Lufaso, A U. Adler, Igor Levin, Juan C. Nino, Virgil Provenzano, Peter K. Schenck, Robert S. Roth
Subsolidus phase relations have been determined for the Bi-Mn-Nb-O system in air (750-900 C). Phases containing Mn2+, Mn3+, and Mn4+ were all observed. Ternary compound formation was limited to pyrochlore, which formed a substantial solid solution region

Phase Formation, Crystal Chemistry, and Properties in the Magnetic Dielectric System Bi 2 O 3- Fe 2 O 3- Nb 2 O 5

June 22, 2006
Author(s)
M W. Lufaso, Terrell A. Vanderah, I M. Pazos, Igor Levin, Juan C. Nino, Virgil Provenzano, Peter K. Schenck, Robert S. Roth
Subsolidus phase relations have been determined for the Bi2O3-Fe2O3-Nb2O5 system in air (900-1075 C). Three new ternary phases were observed Bi3Fe0.5Nb1.5O9 with an Aurivillius-type structure, and two phases with approximate stoichiometries Bi17Fe2Nb31O106

Local Structures and Raman Spectra in the Ca(Zr,Ti)O 3 Perovskite Solid Solutions

February 7, 2006
Author(s)
Igor Levin, Eric J. Cockayne, M W. Lufaso, Joseph C. Woicik, James E. Maslar
Local structures and cation distributions in perovskite Ca(Zr, Ti)O3 solid solutions were analyzed using X-ray absorption fine structure and pair-distribution functions obtained from total neutron scattering. The analyses revealed that the Zr-O and Ti-O

Design of Self-Assembled Multiferroic Nanostructures in Epitaxial Films

January 23, 2006
Author(s)
Igor Levin, Jiying Li, Julia Slutsker, Alexander L. Roytburd
An approach for a rational design of self-assembled multiferroic nanostructures with controlled phase morphologies was demonstrated using the 3-D epitaxial CoFe2O4-PbTiO3 films grown on single-crystal SrTiO3 substrates. The transverse nanostructures

Catalyst-Free Growth of GaN Nanowires

January 1, 2006
Author(s)
Kristine A. Bertness, Norman Sanford, Joy Barker, John B. Schlager, Alexana Roshko, Albert Davydov, Igor Levin
We have grown GaN and AlGaN nanowires on Si (111) substrates with gassource molecular beam epitaxy (MBE). No metal catalysts were used. The nanowires displayed a number of interesting materials properties, including room-temperature luminescence intensity

High Degree of Crystalline Perfection in Spontaneously Grown GaN Nanowires

January 1, 2006
Author(s)
Kristine A. Bertness, Alexana Roshko, Albert Davydov, Igor Levin, Mark D. Vaudin, Joy Barker, John B. Schlager, Norman Sanford, Larry Robins
We have grown a variety of isolated GaN nanowires using gas-source molecular beam epitaxy (MBE) and characterized their structural and optical properties. The nanowires have demonstrated a number of promising materials characteristics, including low defect

Effect of Nitrogen on Band Alignment in HfSiON Gate Dielectrics

November 22, 2005
Author(s)
Safak Sayan, Nhan V. Nguyen, James R. Ehrstein, James J. Chambers, Mark R. Visokay, Manuel Quevedo-Lopez, Luigi Colombo, T Yoder, Igor Levin, Daniel Fischer, M Paunescu, Ozgur Celik, Eric Garfunkel
We have studied the band alignment of HfSiO and HfSiON films by soft x-ray photoemission (SXPS), oxygen K-edge x-ray absorption (XAS), and spectroscopic ellipsometry. Nitridation of HfSiO reduced the band gap by 1.50+- 0.05eV and the valence and conduction

Optical Bandgaps and Composition Dependence of Hafnium Aluminate Thin Films grown by Atomic Layer Chemical Vapor Deposition

November 17, 2005
Author(s)
Nhan V. Nguyen, Safak Sayan, Igor Levin, James R. Ehrstein, I.J.R. Baumvol, C. Driemeier, L Wielunski, Pui-Yee Hung, Alain C. Diebold
Hafnium-aluminate (HfAlO) films grown on Si by Atomic Layer Chemical Vapor Deposition (ALCVD) of different aluminum contents were investigated in this article. Vacuum Ultra-Violet Spectroscopic Ellipsometry (VUV-SE), high Resolution Transmission Electron

The Relation between Crystalline Phase, Electronic Structure and Dielectric Properties in High-K Gate Stacks

September 28, 2005
Author(s)
Safak Sayan, Mark Croft, Nhan Van Nguyen, Tom Emge, James R. Ehrstein, Igor Levin, John S. Suehle, Robert A. Bartynski, Eric Garfunkel
As high permittivity dielectrics approach use in metal-oxide-semiconductor field effect transistor (MOSFET) production, an atomic level understanding of their electronic, and dielectric properties are being rigorously examined. The valence and conduction

Growth habits and defects in ZnO nanowires grown on GaN/sapphire substrates

August 31, 2005
Author(s)
Igor Levin, Albert Davydov, Babak Nikoobakht, Norman Sanford, Pavel Mogilevsky
Growth habits and defects in epitaxial ZnO nanowires grown from Au catalyst on (00.1) GaN/sapphire substrate using the vapor-liquid-solid (VLS) technique were studied using electron microscopy and x-ray diffraction. The results revealed presence of both

Growth Habits and Defects in ZnO Nanowires Grown on GaN/Sapphire Substrates

August 31, 2005
Author(s)
Igor Levin, Albert Davydov, Babak Nikoobakht, Norman A. Sanford, Pavel Mogilevsky
Growth habits and defects in epitaxial ZnO nanowires grown from Au catalyst on (0001) GaN/sapphire substrate using Vapor-Liquid-Solid (VLS) technique were studied using electron microscopy and X-ray diffraction. The results revealed presence of both

First-Order Raman Spectra of AB' 1/2 B'' 1/2 O 3 Double Perovskites

June 1, 2005
Author(s)
S A. Prosandeev, U Waghmare, Igor Levin, James E. Maslar
First principles computations of Raman intensities were performed for perovskite-like compound CaAl1/2Nb1/2O3 (CAN). This compound features 1:1 (NaCl-type) ordering of Al and Nb superimposed onto the b-b-c+ octahedral tilting. Raman tensor for CAN was

Fabrication and Analysis of GaN Nanorods grown by MBE

January 1, 2005
Author(s)
Norman Sanford, Larry Robins, Matthew H. Gray, J E. Van Nostrand, C Stutz, R Cortez, Albert Davydov, Alexander J. Shapiro, Igor Levin, Alexana Roshko
GaN nanorods were grown on c-plane sapphire substrates under N-rich conditions by plasma-assisted molecular-beam epitaxy. Scanning electron microsopy revealed densely packed nanorods of hexagonal cross section with diameters ranging from roughly 40 to 100

Refractive index and birefringence of InGaN films grown by MOCVD

January 1, 2005
Author(s)
Norman Sanford, Anneli Munkholm, Mike A. Krames, Alexander J. Shapiro, Igor Levin, Albert Davydov, Safak Sayan, L Wielunski, T E. Madey
The refractive index and birefringence of InxGa1'xN films grown on GaN layers were measured by prism coupling used in conjunction with multilayer optical waveguide analysis. Samples with x = 0.036, 0.049, 0.060, and 0.066 were examined at the separate

Crystal Chemistry and Crystallography of the Aurivillius Phase Bi 5 AgNb 4 O 18

October 18, 2004
Author(s)
Winnie K. Wong-Ng, Qingzhen Huang, Lawrence P. Cook, Igor Levin, James A. Kaduk, Alan D. Mighell, J Suh
Bi 5AgNb 4O 18 is a new phase, which was discovered during the phase equilibrium study of the Bi 2O 3-Ag 2O-Nb 2O 5 system. Bi 5AgNb 4O 18 was prepared at 750 C and is stable in air up to its melting temperature of 1160.1 5.0 C. Results of a Rietveld

Phase Equilibria of Ba-R-Cu-O-F-OH for Coated-Conductor Applications (R=Lanthanides and Y)

August 1, 2004
Author(s)
Winnie K. Wong-Ng, Lawrence P. Cook, Igor Levin, J Suh, Ron Feenstra, T J. Haugan, P. D. Barnes
Phase diagrams of the Ba 2RCu 3O 6+x (R=Nd, Sm, Gd, Y, and Er) superconductors, prepared under 0.1 % 0 2 at 810 C, reflect the trend of the lanthanide contraction. The single-phase regions of Ba 2-x(Nd 1+x-yR y) Cu 3O 6+z for R=Gd, Y and Yb, and Ba 2-x(R 1