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13 Aug 2001

Volume 79, Issue 7, pp. 895-1063

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In situ multiphase fluid experiments in hydrothermal carbon nanotubes

Yury Gogotsi, Joseph A. Libera, Almila Güvenç-Yazicioglu, and Constantine M. Megaridis

Appl. Phys. Lett. 79, 1021 (2001); http://dx.doi.org/10.1063/1.1391228 (3 pages) | Cited 104 times

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Hydrothermal multiwall closed carbon nanotubes are shown to contain an encapsulated multiphase aqueous fluid, thus offering an attractive test platform for unique in situ nanofluidic experiments in the vacuum of a transmission electron microscope. The excellent wettability of the graphitic inner tube walls by the aqueous liquid and the mobility of this liquid in the nanotube channels are observed. Complex interface dynamic behavior is induced by means of electron irradiation. Strong atomic-scale interactions between the entrapped liquid phase and the wetted terminated graphite layers are revealed by means of high-resolution electron microscopy. The documented phenomena in this study demonstrate the potential of implementing such tubes in future nanofluidic devices. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
47.85.Np Fluidics

Effects of Nb addition on icosahedral quasicrystalline phase formation and glass-forming ability of Zr–Ni–Cu–Al metallic glasses

Cang Fan, Chunfei Li, Akihisa Inoue, and Volker Haas

Appl. Phys. Lett. 79, 1024 (2001); http://dx.doi.org/10.1063/1.1391396 (3 pages) | Cited 13 times

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This work shows that the crystallization process of Zr–Ni–Cu–Al metallic glass is greatly influenced by adding Nb as an alloying element. Based on the results of the differential scanning calorimetry experiments for metallic glasses Zr69−xNbxNi10Cu12Al9 (x = 0–15 at. %), the crystallization process takes place through two individual stages. For Zr69Ni10Cu12Al9 (x = 0), metastable hexagonal ω-Zr and a small fraction of tetragonal Zr2Cu are precipitated upon completion of the first exothermic reaction. Contrary to this alloy, the precipitation of a nanoquasicrystalline phase is detected when 5–10 at. % Nb is added. Furthermore, the crystallization temperature Tx, supercooled liquid region ΔTx and reduced temperature Tg/TL (Tg is the glass transition temperature, TL the liquidus temperature) increase with increasing Nb content. These results indicate that adding Nb content to Zr–Ni–Cu–Al metallic glasses not only induces quasicrystalline phase formation, but also enhances glass-forming ability. © 2001 American Institute of Physics.
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61.44.Br Quasicrystals
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Temporal evolution of GaSb/GaAs quantum dot formation

L. Müller-Kirsch, R. Heitz, U. W. Pohl, D. Bimberg, I. Häusler, H. Kirmse, and W. Neumann

Appl. Phys. Lett. 79, 1027 (2001); http://dx.doi.org/10.1063/1.1394715 (3 pages) | Cited 27 times

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The formation of GaSb quantum dots in a GaAs matrix in the Stranski–Krastanow growth mode under metalorganic chemical vapor deposition conditions is investigated. Transmission electron microscopical images and photoluminescence measurements show the islands to nucleate during the GaSb deposition and to grow subsequently by mass transfer from the two-dimensional wetting layer. The evolving surface morphology indicates local equilibria between quantum dots and the surrounding wetting layer regions. © 2001 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
81.07.Ta Quantum dots
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Lp Transmission electron microscopy (TEM)
78.55.Cr III-V semiconductors

Strain effect in large silicon nanocrystal quantum dots

A. Thean and J. P. Leburton

Appl. Phys. Lett. 79, 1030 (2001); http://dx.doi.org/10.1063/1.1392309 (3 pages) | Cited 14 times

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We present a computer simulation of strain effects on the electronic spectrum of 100 Å diam Si nanocrystal (nc-Si) quantum dots embedded in SiO2, based on the continuum strain model and deformation potential theory. We show that the coupling between the nc-Si geometry and the symmetry generated by the strain potential can enhance confinement in the quantum dot and can lift the degeneracy of the conduction band valleys for nonspherically symmetric nanocrystals. © 2001 American Institute of Physics.
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73.21.La Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)

Stark effect and polarizability in a single CdSe/ZnSe quantum dot

J. Seufert, M. Obert, M. Scheibner, N. A. Gippius, G. Bacher, A. Forchel, T. Passow, K. Leonardi, and D. Hommel

Appl. Phys. Lett. 79, 1033 (2001); http://dx.doi.org/10.1063/1.1389504 (3 pages) | Cited 53 times

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The quantum-confined Stark effect in a single self-assembled CdSe/ZnSe quantum dot was studied by means of highly spatially resolved photoluminescence spectroscopy. A nanotechnological approach making use of a capacitor-like geometry enabled us to apply a well-defined lateral electric field on the quantum dots. Stark shifts of up to 1.1 meV were obtained, which can be well fitted by a purely quadratic dependence on an electric field. In quite good agreement with theoretical calculations, an exciton polarizability of 4.9×10−3 meV/(kV/cm)2 can be extracted, while the permanent dipole moment in the lateral direction is found to be negligible. © 2001 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.67.Hc Quantum dots
78.20.Jq Electro-optical effects
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Hf II-VI semiconductors
71.35.-y Excitons and related phenomena

Collective emission degradation behavior of carbon nanotube thin-film electron emitters

L. Nilsson, O. Groening, P. Groening, and L. Schlapbach

Appl. Phys. Lett. 79, 1036 (2001); http://dx.doi.org/10.1063/1.1392982 (3 pages) | Cited 28 times

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The current-induced emission degradation of a carbon nanotube (CNT) thin-film electron emitter is studied under constant emission current for different current levels, using a scanning anode field emission microscope. A permanent emission degradation is observed for emission currents higher than 300 nA per CNT and is associated with resistive heating at the CNT–substrate interface for the sample under investigation. A second field-induced emission degradation mechanism, associated with the removal of CNTs from the substrate, is also reported. © 2001 American Institute of Physics.
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85.45.Db Field emitters and arrays, cold electron emitters
85.35.Kt Nanotube devices
79.70.+q Field emission, ionization, evaporation, and desorption
73.63.Fg Nanotubes
85.45.Fd Field emission displays (FEDs)
68.37.Vj Field emission and field-ion microscopy

Fabrication of highly ordered metallic nanowire arrays by electrodeposition

A. J. Yin, J. Li, W. Jian, A. J. Bennett, and J. M. Xu

Appl. Phys. Lett. 79, 1039 (2001); http://dx.doi.org/10.1063/1.1389765 (3 pages) | Cited 156 times

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Highly ordered hexagonal arrays of parallel metallic nanowires (Ni, Bi) with diameters of about 50 nm and lengths up to 50 μm were synthesized by electrodeposition. Hexagonal-close-packed nanochannel anodized aluminum oxide film was used as the deposition template. The deposition was performed in an organic bath of dimethylsulfoxide with metal chloride as the electrolyte. A high degree of ordering and uniformity in these arrays can be obtained with this technique by fine-tuning the electrodeposition parameters. Moreover, an unprecedentedly high level of uniformity and control of the wire length was achieved. The arrays are unique platforms for explorations of collective behavior in coupled mesoscopic systems, and are useful for applications in high-density data storage, field emission displays, and sensors. © 2001 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys
81.15.Pq Electrodeposition, electroplating
82.45.Qr Electrodeposition and electrodissolution
61.46.-w Structure of nanoscale materials

Control of nanocrystalline orientation using the application of a stress field in an amorphous alloy

A. Ogura, R. Tarumi, M. Shimojo, K. Takashima, and Y. Higo

Appl. Phys. Lett. 79, 1042 (2001); http://dx.doi.org/10.1063/1.1395526 (3 pages) | Cited 11 times

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Precipitation of nanocrystals in a Ni–P amorphous alloy film during application of a stress field has been investigated. Microsized cantilever-beam-type specimens were prepared from the film by focused-ion-beam machining and bending stress was applied to the specimen using a mechanical testing machine for microsized specimens. Transmission electron microscopy observation in the plane strain deformed region has revealed that the deformation induces the precipitation of nanocrystalline Ni particles, and a (111) plane of all crystalline particles is aligned parallel to the side surface of the specimen. This suggests that control of the nanocrystalline orientation in amorphous alloys would be possible using the application of a stress field. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
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