教師著作

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Browsing 教師著作 by Author "A. Datta"

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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.
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    Enhanced Dynamic Annealing in Ga+ ion-implanted GaN Nanowires
    (American Institute of Physics(AIP) Publishing, 2003-01-20) S. Dhara; A. Datta; C.-T. Wu; Z.-H. Lan; K.-H. Chen; Y.-L. Wang; L.-C. Chen; C.-W. Hsu; H.-M. Lin; Chia-Chun Chen
    Ga+ion implantation of chemical-vapor-deposited GaNnanowires (NWs) is studied using a 50-keV Ga+focused ion beam. The role of dynamic annealing (defect-annihilation) is discussed with an emphasis on the fluence-dependent defect structure. Unlike heavy-ion-irradiated epitaxialGaN film, large-scale amorphization is suppressed until a very high fluence of 2×1016 ions cm−2. In contrast to extended-defects as reported for heavy-ion-irradiated epitaxialGaN film, point-defect clusters are identified as major component in irradiated NWs. Enhanced dynamic annealing induced by high diffusivity of mobile point-defects in the confined geometry of NWs is identified as the probable reason for observed differences.
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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.