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Search Publications by: Igor Levin ()

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Displaying 51 - 75 of 132

Ferri- to ferro-magnetic transition in the martensitic phase of a Heusler alloy

September 15, 2012
Author(s)
Robert D. Shull, Lawrence H. Bennett, Virgil Provenzano, Y. N. Jin, Igor Levin, E. Della Torre
During the past decade the magnetic properties of Heusler alloys have been extensively studied, motivated in part by the observation of large magnetocaloric effect (MCE) peaks displayed by these alloys near room temperature. We present new data and

Ti_(12.5)Zr_(21)V_(10)Cr_(8.5)Mn_(x)Co_(1.5)Ni_(46.5-x)AB_(2)-type metal hydride alloys for electrochemical storage application: Part 1. Structural characteristics

August 3, 2012
Author(s)
Leonid A. Bendersky, Ke Wang, Igor Levin, Dale E. Newbury, K. Young, B. Chao, Adam A. Creuziger
The microstructures of a series of AB_(2)-based metal hydride alloys (Ti_(12.5)Zr_(21)V_(10)Cr_(8.5)Mn_(x)Co_(1.5)Ni_(46.5-x)) designed to have different fractions of non-Laves secondary phases were studied by x-ray diffraction, scanning electron

Ultimate bending strength of Si nanowires

April 11, 2012
Author(s)
Gheorghe Stan, Sergiy Krylyuk, Albert Davydov, Igor Levin, Robert F. Cook
Test platforms for the ideal strength of materials are provided by almost defect-free nanostructures (nanowires, nanotubes, nanoparticles, for example). In this work, the ultimate bending strengths of Si nanowires with radii in the 20 nm to 60 nm range

Crystal Structure of the Type I Clathrate Ba8Ni4Ge42

March 30, 2012
Author(s)
Winnie K. Wong-Ng, Qingzhen Huang, Igor Levin, Joseph C. Woicik, Xun Shi, Jihui Yang, James A. Kaduk
The crystal structure of Type-I clathrate Ba8Ni4Ge42 has been determined using neutron powder diffraction, transmission electron microscopy (TEM, for possible superlattice), extended X-ray absorption fine structure measurements. Ba8Ni4Ge42 is cubic with

Effect of AlN Buffer Layer Properties on the Morphology and Polarity of GaN Nanowires Grown by Molecular Beam Epitaxy

September 8, 2011
Author(s)
Matthew D. Brubaker, Kristine A. Bertness, Norman A. Sanford, Albert Davydov, Igor Levin, Devin M. Rourke, Victor M. Bright
Low temperature AlN buffer layers grown by plasma-assisted Molecular Beam Epitaxy (MBE) on Si (111) were found to significantly affect the subsequent growth morphology of GaN nanowires. The AlN buffer layers exhibited nanowire-like columnar protrusions

Tapering Control of Si Nanowires Grown from SiCl4 at Reduced Pressure

December 15, 2010
Author(s)
Sergiy Krylyuk, Albert Davydov, Igor Levin
Device applications of tapered Si nanowire (SiNW) arrays require reliable technological approaches for fabricating nanowires with controlled shape and orientation. In this study, we systematically explore effects of growth conditions on tapering of Si

Enhanced Mass Transport in Ultra-Rapidly-Heated Ni/Si Thin-Film Multilayers

November 15, 2009
Author(s)
Lawrence P. Cook, Richard E. Cavicchi, Nabil Bassim, Susie Eustis, Winnie Wong-Ng, Igor Levin, Ursula R. Kattner, Carelyn E. Campbell, Christopher B. Montgomery, William F. Egelhoff Jr., Mark D. Vaudin
We have investigated multilayer and bilayer Ni/Si thin films by nano-differential scanning calorimetry (DSC) at ultra rapid scan rates, in a temperature-time regime not accessible with conventional apparatus. DSC experiments were completed at slower scan

A Combined Fit of Total Scattering and Extended X-ray Absorption Fine Structure Data for Local-Structure Determination in Crystalline Materials

October 5, 2009
Author(s)
Igor Levin, Victor L. Krayzman, Joseph C. Woicik, Terrell A. Vanderah, M. G. Tucker, Thomas Proffen
Reverse Monte Carlo (RMC) refinements of local structure using a simultaneous fit of x-ray/neutron total scattering and EXAFS data were developed to incorporate an explicit treatment of both single- and multiple-scattering contributions to EXAFS. The

Structural Changes behind the Diffuse Dielectric Response in AgNbO3

March 13, 2009
Author(s)
Igor Levin, Victor L. Krayzman, Joseph C. Woicik, J. Karapetrova, T. Proffen, M. G. Tucker, I. M. Reaney
Structural changes among the so-called M-polymorphs of AgNbO3 were analyzed using combined high-resolution X-ray diffraction, neutron total scattering, electron diffraction, and X-ray absorption fine structure measurements. These polymorphs crystallize

Combinatorial Studies of Ba-Y-Cu-O Films for Coated-Conductor Applications

October 23, 2008
Author(s)
Winnie K. Wong-Ng, Makoto Otani, Igor Levin, Peter K. Schenck, Zhi Yang, Guangyao Liu, Lawrence P. Cook, Ron Feenstra, Wei Zheng, Marty Rupich
Phase relationships in bulk and thin film Ba-Y-Cu-O high-Tc superconductor system were determined at processing conditions relevant for industrial production of coated conductors. Our results demonstrated that the absence of BaY2CuO5 (which has a critical

Growth, Crystal Structure, and Properties of Epitaxial BiScO3 Thin Films

August 15, 2008
Author(s)
Igor Levin, Susan Trolier-McKinstry, Michael D. Biegalski, Junling Wang, Alexei A. Belik, E. Takayama-Muromachi
Epitaxial thin films of BiScO3, a compound which is thermodynamically unstable under ambient conditions, were grown on BiFeO3-buffered SrTiO3 substrates despite the very large lattice mismatch between the film and the substrate. The epitaxial BiScO3 films

Piezoelectric Response of Nanoscale PbTiO3 in Composite PbTiO3-CoFe2O4 Epitaxial Films

August 15, 2008
Author(s)
Igor Levin, Tan Zhuopeng, Alexander Roytburd, Katyayani Seal, Brian Rodriguez, Stephen Jesse, Sergei Kalinin, Art Baddorf
Piezoelectric properties of PbTiO3 in 1/3PbTiO3-2/3CoFe2O4 transverse epitaxial nanostructures on differently oriented SrTiO3 were analyzed using conventional and switching-spectroscopy piezoelectric force microscopy. The results confirmed that the

Nature of Transition Layers at the SiO 2 /SiC Interface

July 14, 2008
Author(s)
T Zheleva, Aivars Lelis, G Duscher, F Liu, Igor Levin, M Das
Electrical performance of SiC-based microelectronic devices is strongly affected by the densities of interfacial traps introduced by the chemical and structural changes at the SiO2/SiC interfaces during processing. We analyzed the structure and chemistry

Crystal Structure, Stoichiometry, and Dielectric Relaxation in Bi 3.32 Nb 7.09 O 22.7 and Structurally Related Ternary Phases

April 17, 2008
Author(s)
I E. Grey, Terrell A. Vanderah, W G. Mumme, Robert S. Roth, Jorge T. Guzman, Juan C. Nino, Igor Levin
Ceramic materials which exhibit high relative dielectric permittivities and are processible at temperatures in the 1000 C to 1200 C range are of interest for embedded elements such as capacitor, resonators, and filters. Complex titanates, niobates, and

Growth of Silicon Carbide Nanowires by a Microwave Heating-Assisted Physical Vapor Transport Using Group VIII Metal Catalysts

November 13, 2007
Author(s)
Siddarth Sundaresan, Albert Davydov, Mark D. Vaudin, Igor Levin, James E. Maslar, Yong-lai Tian, M V. Rao
SiC nanowires are grown by a novel catalyst-assisted sublimation-sandwich (SS) method. This involves microwave heating-assisted physical vapor transport from a source 4H-SiC wafer to a closely positioned substrate 4H-SiC wafer. The substrate wafer is