教師著作
Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/37076
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Item On-chip Fabrication of Well-aligned and Contact-barrier-free GaN Nanobridge Devices with Ultrahigh Photocurrent Responsivity(Wiley-VCH Verlag, 2008-07-01) R.-S. Chen; S.-W. Wang; Z.-H. Lan; J. T.-H. Tsai; C.-T. Wu; L.-C. Chen; K.-H. Chen; Y.-S. Huang; Chia-Chun ChenBuilding nanobridges: Direct integration of an ensemble of GaN nanowires (n) onto a microchip produces a viable nanobridge (NB) device with good alignment and contact performance, the design of which demonstrates the potential of nanowires for sensor development. These GaN NBs have strong surface-enhanced photoconductivity with ultrahigh responsivityItem High-phase-purity zinc-blende InN on r-plane sapphire substrate with controlled nitridation pretreatment(American Institute of Physics (AIP), 2008-03-17) C.-L. Hsiao; T.-W. Liu; C.-T. Wu; H.-C. Hsu; G.-M. Hsu; L.-C. Chen; W.-Y. Shiao; C.-C. Yang; A. Gaellstroem; P.-O. Holtz; Chia-Chun Chen; K.-H. ChenHigh-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r-plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors.Item Enhanced Emission of (In, Ga) Nitride Nanowires Embedded with Self-assembled Quantum Dots(Wiley-VCH Verlag, 2008-03-25) C.-W. Hsu; A. Ganguly; C.-H. Liang; Y.-T. Hung; C.-T. Wu; G.-M. Hsu; Y.-F. Chen; Chia-Chun Chen; K.-H. Chen; L.-C. ChenWe report the structure and emission properties of ternary (In,Ga)N nanowires (NWs) embedded with self-assembled quantum dots (SAQDs). InGaN NWs are fabricated by the reaction of In, Ga and NH3 via a vapor–liquid–solid (VLS) mechanism, using Au as the catalyst. By simply varying the growth temperature, In-rich or Ga-rich ternary NWs have been produced. X-ray diffraction, Raman studies and transmission electron microscopy reveal a phase-separated microstructure wherein the isovalent heteroatoms are self-aggregated, forming SAQDs embedded in NWs. The SAQDs are observed to dominate the emission behavior of both In-rich and Ga-rich NWs. Temperature-dependent photoluminescence (PL) measurements indicate relaxation of excited electrons from the matrix of the Ga-rich NWs to their embedded SAQDs. A multi-level band schema is proposed for the case of In-rich NWs, which showed an anomalous enhancement in the PL peak intensity with increasing temperature accompanies with red shift in its peak position.Item Self-Regulating and Diameter-Selective Growth of GaN Nanowires(IOP Publishing, 2006-06-14) C.-K. Kuo; C.-W. Hsu; C.-T. Wu; Z.-H. Lan; C.-Y. Mou; Y.-J. Yang; Chia-Chun Chen; K.-H. ChenWe report diameter-selective growth of GaN nanowires (NWs) by using mono-dispersed Au nanoparticles (NPs) on a ligand-modified Si substrate. The thiol-terminal silane was found to be effective in producing well-dispersed Au NPs in low density on Si substrates so that the agglomeration of Au NPs during growth could be avoided. The resultant GaN NWs exhibited a narrow diameter distribution and their mean diameter was always larger than, while keeping a deterministic relation with, the size of the Au NPs from which they were grown. A self-regulating steady growth model is proposed to account for the size-control process.Item Nanohomojunction (GaN) and nanoheterojunction (InN) nanorods on one-dimensional GaN nanowire substrates(Wiley-VCH Verlag, 2004-03-01) Z.-H. Lan; C.-H. Liang; C.-W. Hsu; C.-T. Wu; H.-M. Lin; S. Dhara; K.-H. Chen; L.-C. Chen; Chia-Chun ChenThe formation of homojunctions and heterojunctions on two-dimensional (2D) substrates plays a key role in the device performance of thin films. Accelerating the progress of device fabrication in nanowires (NWs) also necessitates a similar understanding in the one-dimensional (1D) system. Nanohomojunction (GaN on GaN) and nanoheterojunction (InN on GaN) nanorods (NRs) were formed in a two-step growth process by a vapor–liquid–solid (VLS) mechanism. Ga2O3 nanoribbons were formed using Ni as catalyst in a chemical vapor deposition (CVD) technique and then completely converted to GaN NWs with NH3 as reactant gas. An Au catalyst is used in the second step of the VLS process to grow GaN and InN NRs on GaN NWs using CVD techniques. A morphological study showed the formation of nanobrushes with different structural symmetries and sub-symmetries in both homogeneous and heterogeneous systems. Structural characterizations showed nearly defect-free growth of nanohomojunction (GaN) and nanoheterojunction (InN) NRs on 1D GaN NW substrates.Item Blueshift of yellow luminescence band in self-ion-implanted n-GaN nanowire(American Institute of Physics (AIP), 2004-05-03) S. Dhara; A Datta; C.-T. Wu; Z.-H. Lan; K.-H. Chen; Y. -L. Wang; Y.-F. Chen; C.-W. Hsu; L.-C. Chen; H.-M. Lin; Chia-Chun ChenOptical photoluminescence studies are performed in self-ion (Ga+)-implanted nominally dopedn-GaNnanowires. A 50 keV Ga+focused ion beam in the fluence range of 1×1014–2×1016 ions cm−2 is used for the irradiation process. A blueshift is observed for the yellow luminescence (YL) band with increasing fluence. Donor–acceptor pair model with emission involving shallow donor introduced by point-defect clusters related to nitrogen vacancies and probable deep acceptor created by gallium interstitial clusters is responsible for the shift. High-temperature annealing in nitrogen ambient restores the peak position of YL band by removing nitrogen vacancies.Item 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 ChenHexagonal 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.Item 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 ChenStructure 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.Item 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 ChenGa+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.