Xueyin Sun

Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons

Rope-like bundles of single-walled carbon nanotubes (SWNTs) similar to those obtained by laser vaporization and electric-are techniques were synthesized on a relatively large scale and at low cost by the catalytic decomposition of hydrocarbons at a temperature of about 1200 degrees C using an improved floating catalyst method. The SWNTs thus obtained have larger diameters and are self-organized into ropes. The addition of thiophene was found to be effective in promoting the growth of SWNTs and in increasing the yield of either SWNTs or multiwalled carbon nanotubes under different growth conditions

Theoretical modeling of thermoelectricity in Bi nanowires

A theoretical model based on the basic electronic band structure of bulk Bi is developed to predict the dependence of the band structure and thermoelectric properties on nanowire width. By carefully tailoring the Bi wire size and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire widths.

Multiferroic Behavior of Templated BiFeO3–CoFe2O4 Self-Assembled Nanocomposites

Self-assembled BiFeO3-CoFe2O4 nanocomposites were templated into ordered structures in which the ferrimagnetic CoFe2O4 pillars form square arrays of periods 60-100 nm in a ferroelectric BiFeO3 matrix. The ferroelectricity, magnetism, conductivity, and magnetoelectric coupling of the ordered nanocomposites were characterized by scanning probe microscopy. The insulating BiFeO3 matrix exhibited ferroelectric domains, whereas the resistive CoFe2O4 pillars exhibited single-domain magnetic contrast with high anisotropy due to the magnetoelasticity of the spinel phase. Magnetoelectric coupling was observed in which an applied voltage led to reversal of the magnetic pillars.

Integration of bulk-quality thin film magneto-optical cerium-doped yttrium iron garnet on silicon nitride photonic substrates

Cerium substituted yttrium iron garnet (Ce:YIG) films were grown on yttrium iron garnet (YIG) seed layers on silicon nitride films using pulsed laser deposition. Optimal process conditions for forming garnet films on silicon nitride are presented. Bulk or near-bulk magnetic and magneto-optical properties were observed for 160 nm thick Ce:YIG films grown at 640 °C on rapid thermal annealed 40 nm thick YIG grown at 640 °C and 2 Hz pulse rate. The effect of growth temperature and deposition rate on structural, magnetic and magneto-optical properties has been investigated.

Magnetic Phase Formation in Self-Assembled Epitaxial BiFeO3–MgO and BiFeO3–MgAl2O4 Nanocomposite Films Grown by Combinatorial Pulsed Laser Deposition

Self-assembled epitaxial BiFeO3-MgO and BiFeO3-MgAl2O4 nanocomposite thin films were grown on SrTiO3 substrates by pulsed laser deposition. A two-phase columnar structure was observed for BiFeO3-MgO codeposition within a small window of growth parameters, in which the pillars consisted of a magnetic spinel phase (Mg,Fe)3O4 within a BiFeO3 matrix, similar to the growth of BiFeO3-MgFe2O4 nanocomposites reported elsewhere. Further, growth of a nanocomposite with BiFeO3-(CoFe2O4/MgO/MgFe2O4), in which the minority phase was grown from three different targets, gave spinel pillars with a uniform (Mg,Fe,Co)3O4 composition due to interdiffusion during growth, with a bifurcated shape from the merger of neighboring pillars. BiFeO3-MgAl2O4 did not form a well-defined vertical nanocomposite in spite of having lower lattice mismatch, but instead formed a two-phase film with in which the spinel phase contained Fe. These results illustrate the redistribution of Fe between the oxide phases during oxide codeposition to form a ferrimagnetic phase from antiferromagnetic or nonmagnetic targets.

Multispectral pixel performance using a one-dimensional photonic crystal design

A photodetector pixel using a photonic crystal structure incorporating photoconductive layers has been realized. The fabricated device exploits mode discrimination and resonant cavity enhancement to provide simultaneous multispectral detection capability, high quantum efficiency, and dramatically suppressed shot noise. Detectivities as high as 2.6×1010 and 2.0×1010cmHz1∕2W−1 at the two preselected wavelengths, 632 and 728nm, were achieved, respectively.

Magnetism and Faraday Rotation in Oxygen-Deficient Polycrystalline and Single-Crystal Iron-Substituted Strontium Titanate

Taichi Goto, Dong Hun Kim, Xueyin Sun, Mehmet C. Onbasli, Juan M. Florez, Shyue Ping Ong, Patricio Vargas, Karl Ackland, Plamen Stamenov, Nicolas M. Aimon, Mitsuteru Inoue, Harry L. Tuller, Gerald F. Dionne, J. Michael D. Coey, and Caroline A. Ross Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibari-Ga-Oka, Tempaku, Toyohashi 441-8580, Japan Department of Materials Science and Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin, Kyeonggi-do 449-728, Korea School of Materials Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Nan Gang District, Harbin 150001, China Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA Departamento de Física, Universidad Técnica Federico Santa María, España 1680, Valparaíso, P.O. Box 110-V, Chile Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland (Received 18 May 2016; revised manuscript received 31 October 2016; published 8 February 2017)

Multispectral 1-D Photonic Crystal Photodetector

We demonstrate a novel photoconductor pixel, by using a photonic crystal structure incorporating photoconductive layers, which exploits resonant cavity enhancement to provide us with multispectral capability, high quantum efficiency, and dramatically suppressed shot noise