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  • Author(s):
    Robert Hughes, Sergei Rouvimov, Robert Neal, Trevor B. Demille, Svetlana Neretina
    Abstract:

    The seed-mediated growth of noble metal nanostructures with planar geometries requires the use of seeds lined with parallel stacking faults so as to provide a break in symmetry in an otherwise isotropic metal. Although such seeds are now routinely synthesized using colloidal pathways, equivalent pathways have not yet been reported for the fabrication of substrate-based seeds with the same internal defect structures. The challenge is not merely to form seeds with planar defects but to do so in…

    Date Published:
    2019-07
  • Author(s):
    Kazuki Nomoto, Aditya Sundar, Kevin Lee, Mingda Zhu, Zongyang Hu, Edward Beam, Jinqiao Xie, Manyam Pilla, Xiang Gao, Sergei Rouvimov, Debdeep Jena, Huili Grace Xing
    Abstract:

    GaN PolarMOS is a vertical power transistor incorporating the unique polarization-induced bulk doping scheme in III-nitrides for the body p-n junction. We report the realization of this device, wherein the vertical channel, source contact, and body contact regions are successfully formed using three steps of selective-area epitaxial regrowth, all by molecular beam epitaxy (MBE). The fabricated PolarMOS has an excellent on-current of >500 mA mm−1 and a specific on-resistance of 0.66 mΩ · cm…

    Date Published:
    2019-05
  • Author(s):
    Rusen Yan, Guru Khalsa, Brian T. Schaefer, Alexander Janjour, Sergei Rouvimov, Katja Nowack, Huili Xing, Debdeep Jena
    Abstract:

    We report a systematic study of thickness-dependent superconductivity and carrier transport properties in exfoliated layered 2H-NbS2. Hall-effect measurements reveal 2H-NbS2 is a p-type metal with hole mobility of 1–3 cm2 V−1 s−1. The superconducting transition temperature is found to decrease with thickness. However, we find that superconductivity is suppressed due to disorder resulting from the incorporation of atmospheric oxygen. Cross-section transmission electron microscope imaging revea…

    Date Published:
    2019-02
  • Author(s):
    Spencer Golze, Robert Neal, Robert Hughes, Svetlana Neretina, Sergei Rouvimov
    Abstract:

    Not Available

  • Author(s):
    Eredzhep Menumerov, Robert Hughes, Spencer Golze, Robert Neal, Trevor Demille, Justin Campanaro, Kyle Kotecky, Sergei Rouvimov, Svetlana Neretina
    Abstract:

    The fundamental understanding of liquid-phase catalytic reactions is unavoidably complicated when the catalyst is prone to leaching since questions inevitably arise as to the true nature of the catalyst. While the catalytic reduction of 4-nitrophenol by borohydride is widely accepted as a trusted model reaction, it has faced little scrutiny concerning the potential impact of leached species or the appropriateness of assigning catalytic activity to the inserted nanostructures without rigorous …

    Date Published:
    2018
  • Author(s):
    Valentin Jmerik, Dmitrii Nechaev, Alexey Toropov, Evgenii Evropeitsev, Vladimir Kozlovsky, Victor Martovitsky, Sergei Rouvimov, Sergei Ivanov
    Abstract:

    We report the internal structures and emission properties of GaN/AlN single- and multiple-quantum-well (QW) heterostructures with well widths of d w = 1–4 monolayers (MLs), grown by plasma-assisted molecular-beam epitaxy on c-sapphire at metal-rich conditions and low temperatures (~700 °C). The formation of plane QWs with abrupt symmetrical interfaces is confirmed by both scanning transmission electron microscopy and X-ray diffraction analysis. Pulse-scanning and continuous-wave output powers…

    Date Published:
    2018
  • Author(s):
    Joseph A Hagmann, Xiang Li, Sugata Chowdhury, Si-Ning Dong, Sergei Rouvimov, Sujitra J Pookpanratana, Kin Man Yu, Tatyana A Orlova, Trudy B Bolin, Carlo U Segre
    Abstract:

    We demonstrate that the introduction of an elemental beam of Mn during the molecular beam epitaxial growth of Bi2Se3 results in the formation of layers of Bi2MnSe4 that intersperse between layers of pure Bi2Se3. This study revises the assumption held by many who study magnetic topological insulators (TIs) that Mn incorporates randomly at Bi-substitutional sites during epitaxial growth of Mn:Bi2Se3. Here, we report the formation of thin film magnetic TI Bi2MnSe4 with stoichiometric composition…

    Date Published:
    2017
  • Author(s):
    Vasily Kanzyuba, Sining Dong, Xinyu Liu, Xiang Li, Sergei Rouvimov, Hanako Okuno, Henri Mariette, Xueqiang Zhang, Sylwia Ptasinska, Brian D. Tracy, David J. Smith, Margaret Dobrowolska, Jacek K. Furdyna
    Abstract:

    We describe the structural evolution of dilute magnetic (Sn,Mn)Se films grown by molecular beam epitaxy on GaAs (111) substrates, as revealed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. When the Mn concentration is increased, the lattice of the ternary (Sn,Mn)Se films evolves quasi-coherently from a SnSe2 two-dimensional (2D) crystal structure into a more complex quasi-2D lattice rearrangement, ultimately transforming into the magnetically con…

    Date Published:
    2017
  • Author(s):
    A.A. Toropov, E.A. Evropeytsev, V.N. Jmerik, D.V. Nechaev, S.V. Ivanov, Sergei Rouvimov
    Abstract:

    A few monolayer-thick (ML) GaN quantum well (QW) structures are promising for high-power optoelectronic applications in mid-UV wavelength ranges [1-2]. High Resolution Transmission Electron Microscopy (HRTEM) and especially High Angle Annual Dark Field (HAADF) Transmission Electron Microscopy (STEM) appear to be a key metrology to establish a relationship between atomic structure and optical properties of nanostructures. TEM/STEM also provides an effective pathway for optimization of crystal …

    Date Published:
    2017
  • Author(s):
    Khachatur V. Manukyan, Armenuhi V. Yeghishyan, Vardan Danghyan, Sergei Rouvimov, Alexander S. Mukasyan, Eduardo E. Wolf
    Abstract:

    In this work, we report a liquid-phase reduction method to prepare porous non-supported amorphous nickel catalysts with high surface areas (65–250 m2/g). A highly crystalline face center cubic Ni (fcc-Ni) catalyst with 110 m2/g surface area was also prepared by frontal crystallization of the amorphous nickel catalyst. The catalytic activity and stability of these catalysts for ethanol decomposition was investigated at different time on stream (TOS) to understand structural transformations occ…

    Date Published:
    2018