Yong Kim

Publications (34) View all

• Article: Phase separation induced by Au catalysts in ternary InGaAs nanowires.

  Yanan Guo, Hong-Yi Xu, Graeme John Auchterlonie, Timothy Burgess, Hannah Joyce, Michael Gao, Hark Hoe Tan, C Jagadish, Haibo Shu, Xiao Shuang Chen, Wei Lu, Yong Kim, Jin Zou
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  ABSTRACT: We report a novel phase separation phenomenon observed in the growth of ternary InxGa1-xAs nanowires by metalorganic chemical vapor deposition. A spontaneous formation of core-shell nanowires is investigated by cross-sectional transmission electron microscopy, revealing the compositional complexity within the ternary nanowires. It has been found that, for InxGa1-xAs nanowires, high precursor flow rates generate ternary InxGa1-xAs cores with In-rich shells, while low precursor flow rates produce binary GaAs cores with ternary InxGa1-xAs shells. First-principle calculations combined with thermodynamic considerations suggest that this phenomenon is due to competitive alloying of different group-III elements with Au catalysts, and variations in elemental concentrations of group-III materials in the catalyst under different precursor flow rates. This study shows that precursor flow rates are critical factors for manipulating Au catalysts to produce nanowires of desired composition.
  Nano Letters 01/2013; · 13.20 Impact Factor
• Article: Taper-free and kinked germanium nanowires grown on silicon via purging and the two-temperature process.

  Jung Hyuk Kim, So Ra Moon, Yong Kim, Zhi Gang Chen, Jin Zou, Duk Yong Choi, Hannah J Joyce, Qiang Gao, H Hoe Tan, Chennupati Jagadish
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  ABSTRACT: We investigate the growth procedures for achieving taper-free and kinked germanium nanowires epitaxially grown on silicon substrates by chemical vapor deposition. Singly and multiply kinked germanium nanowires consisting of <111> segments were formed by employing a reactant gas purging process. Unlike non-epitaxial kinked nanowires, a two-temperature process is necessary to maintain the taper-free nature of segments in our kinked germanium nanowires on silicon. As an application, nanobridges formed between (111) side walls of V-grooved (100) silicon substrates have been demonstrated.
  Nanotechnology 03/2012; 23(11):115603. · 3.98 Impact Factor
• Article: Defect-Free GaAs/AlGaAs Core–Shell Nanowires on Si Substrates

  Jung-Hyun Kang, Qiang Gao, Hannah J. Joyce, Hark Hoe Tan, Chennupati Jagadish, Yong Kim, Yanan Guo, Hongyi Xu, Jin Zou, Melodie A. Fickenscher, Leigh M. Smith, Howard E. Jackson, Jan M. Yarrison-Rice
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  ABSTRACT: We report straight and vertically aligned defect-free GaAs nanowires grown on Si(111) substrates by metal–organic chemical vapor deposition. By deposition of thin GaAs buffer layers on Si substrates, these nanowires could be grown on the buffer layers with much less stringent conditions as otherwise imposed by epitaxy of III–V compounds on Si. Also, crystal-defect-free GaAs nanowires were grown by using either a two-temperature growth mode consisting of a short initial nucleation step under higher temperature followed by subsequent growth under lower temperature or a rapid growth rate mode with high source flow rate. These two growth modes not only eliminated planar crystallographic defects but also significantly reduced tapering. Core–shell GaAs–AlGaAs nanowires grown by the two-temperature growth mode showed improved optical properties with strong photoluminescence and long carrier life times.
  05/2011;
• Conference Proceeding: Structural and optical characterization of vertical GaAs/GaP core-shell nanowires grown on Si substrates

  Jung-Hyun Kang, Qiang Gao, H.J. Joyce, Yong Kim, Yanan Guo, Hongyi Xu, Jin Zou, M.A. Fickenscher, L.M. Smith, H.E. Jackson, J.M. Yarrison-Rice, H.H. Tan, C. Jagadish
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  ABSTRACT: GaAs nanowires were grown on Si (111) substrates. By coating a thin GaAs buffer layer on Si surface and using a two-temperature growth, the morphology and crystal structure of GaAs nanowires were dramatically improved. The strained GaAs/GaP core-shell nanowires, based on the improved GaAs nanowires with a shell thickness of 25 nm, showed a significant shift in emission energy of 260 meV from the unstrained GaAs nanowires.
  Optoelectronic and Microelectronic Materials and Devices (COMMAD), 2010 Conference on; 01/2011
• Conference Proceeding: Improvement of morphology, structure, and optical properties of GaAs nanowires grown on Si substrates

  Jung-Hyun Kang, Qiang Gao, H.J. Joyce, H.H. Tan, C. Jagadish, Yong Kim, Yanan Guo, Hongyi Xu, Jin Zou, M.A. Fickenscher, L.M. Smith, H.E. Jackson, J.M. Yarrison-Rice
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  ABSTRACT: We investigate vertical and defect-free growth of GaAs nanowires on Si (111) substrates via a vapor-liquid-solid (VLS) growth mechanism with Au catalysts by metal-organic chemical vapor deposition (MOCVD). By using annealed thin GaAs buffer layers on the surface of Si substrates, most nanowires are grown on the substrates straight, following (111) direction; by using two temperature growth, the nanowires were grown free from structural defects, such as twin defects and stacking faults. Systematic experiments about buffer layers indicate that V/III ratio of precursor and growth temperature can affect the morphology and quality of the buffer layers. Especially, hetero-structural buffer layers grown with different V/III ratios and temperatures and in-situ post-annealing step are very helpful to grow well arranged, vertical GaAs nanowires on Si substrates. The initial nanowires having some structural defects can be defect-free by two-temperature growth mode with improved optical property, which shows us positive possibility for optoelectronic device application.
  Nanotechnology (IEEE-NANO), 2010 10th IEEE Conference on; 09/2010