教師著作

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Author: search.filters.author.C.-H. ShenHas files: No

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    Hexagonal-to-Cubic Phase Transformation in GaN Nanowires by Ga+ Implantation
    (American Institute of Physics (AIP), 2004-06-28) S. Dahara; A. Datta; C.-T. Wu; Z.-H. Lan; K.-H. Chen; Y. -L. Wang; C.-W. Hsu; C.-H. Shen; L.-C. Chen; Chia-Chun Chen
    Hexagonal to cubic phase transformation is studied in focused ion beam assisted Ga+-implanted GaNnanowires. Optical photoluminescence and cathodoluminescence studies along with high-resolution transmission electron microscopic structural studies are performed to confirm the phase transformation. In one possibility, sufficient accumulation of Ga from the implanted source might have reduced the surface energy and simultaneously stabilized the cubic phase. Another potential reason may be that the fluctuations in the short-range order induced by enhanced dynamic annealing (defect annihilation) with the irradiation process stabilize the cubic phase and cause the phase transformation.
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    Electronic Structure of GaN Nanowire Studied by x-ray-Absorption Spectroscopy and Scanning Photoelectron Microscopy
    (American Institute of Physics(AIP) Publishing, 2003-06-02) J.-W. Chiou; J.-C. Jan; H.-M. Tsai; W.-F. Pong; M.-H. Tsai; I.-H. Hong; R. Rklauser; J.-F. Lee; C.-W. Hsu; H.-M. Lin; Chia-Chun Chen; C.-H. Shen; L.-C. Chen; K.-H. Chen
    X-ray absorption near edge structure (XANES) and scanning photoelectron microscopy (SPEM) measurements have been employed to obtain information on the electronic structures of the GaN nanowires and thin film. The comparison of the XANES spectra revealed that the nanowires have a smaller (larger) N (Ga) K edge XANES intensity than that of the thin film, which suggests an increase (decrease) of the occupation of N 2p (Ga 4p) orbitals and an increase of the N (Ga) negative (positive) effective charge in the nanowires. The SPEM spectra showed that the Ga 3d band for the nanowires lies about 20.8 eV below the Fermi level and has a chemical shift of about -0.9 eV relative to that of the thin film. © 2003 American Institute of Physics.
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    Characterization of Nanodome on GaN Nanowires Formed with Ga Ion Irradiation
    (Nihon Kinzoku Gakkai, 2004-01-01) S. Muto; S. Dahara; A. Datta; C.-W. Hsu; C.-T. Wu; C.-H. Shen; L. -C. Chen; K.-H. Chen; Y.-L. Wang; T. Tanabe; T. Maruyama; H.-M. Lin; Chia-Chun Chen
    Structure of nano-domes formed by Ga+ ion irradiation with a focused ion beam (FIB) apparatus onto GaN nanowires (NWs) was examined with conventional transmission electron microscopy (CTEM), electron energy-loss spectroscopy (EELS) and energy-filtering TEM (EF-TEM). The nano-dome consisted of metallic gallium, covered by a GaN layer, the structure of which is amorphous or liquid. It is considered that the dome structure is formed by preferential displacement of lighter element (N) and agglomeration of heavier one (Ga). 1 MeV electron irradiation onto the sample pre-irradiated by Ga+ ions at a dose below the threshold for the dome formation induced the N2 bubble formation without segregating Ga atoms, which suggests the radiation-enhanced diffusion (RED) of heavy atoms plays an important role in the nano-dome formation.