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1 Aug 2004

Volume 96, Issue 3, pp. 1283-1768

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Control of growth mode in SrTiO3 homoepitaxy under 500°C

Yan Rong Li, Jin Long Li, Ying Zhang, Xian Hua Wei, Xin Wu Deng, and Xing Zhao Liu

J. Appl. Phys. 96, 1640 (2004); http://dx.doi.org/10.1063/1.1763987 (4 pages) | Cited 6 times

Online Publication Date: 26 July 2004

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Homoepitaxial SrTiO3 thin films were grown by laser molecular beam epitaxy. The growth mode was determined by in-situ reflective high energy electron diffraction, and the surface of the films was studied by ex-situ atomic force microscopy. At the deposition rate of 0.16math∕sec and the laser energy density of 6J∕cm2, layer-by-layer growth was observed above 460 °C substrate temperature, while the Stranski-Krastanov growth mode, that is layer-by-layer growth plus island growth mode, prevailed between 460 °C and 410 °C. On further decreasing the substrate temperature, the island growth was determined under 410 °C. With the optimization of deposition process in terms of laser energy density and deposition rate, the lowest crystallization temperatures of SrTiO3 films grown in layer-by-layer growth mode were obtained as low as 280°C. The effects of laser energy density on growth temperature were studied.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Fg Pulsed laser ablation deposition
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.37.Ps Atomic force microscopy (AFM)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Inhomogeneous strain state in a rectangular InGaAs quantum wire/GaAs barrier specimen prepared for cross sectional high-resolution transmission electron microscopy

Yo-Han Yoo, Woong Lee, and Hyunho Shin

J. Appl. Phys. 96, 1644 (2004); http://dx.doi.org/10.1063/1.1763995 (5 pages) | Cited 1 time

Online Publication Date: 26 July 2004

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Inhomogeneous strain state in a rectangular InGaAs quantum wire (QWR) embedded in GaAs matrix has been comparatively studied, via finite element analysis, for the cases of specimen prepared for high-resolution transmission electron microscopy (HRTEM) and the bulk specimen. The quantum wire is extruded from the surface of the HRTEM specimen due to the inherent lattice-mismatch strain, which yields an inhomogeneous strain state in the HRTEM specimen. Some strain components are significantly relaxed in the HRTEM specimen, while other one is comparable to the strain state in bulk counterpart, depending on strain-monitoring location. Thus, careful selection of the strain component and measuring location is necessary in order to get meaningful bulk strain information from the HRTEM specimen, which is informative for the analysis and design of the QWR nanostructures.
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61.46.-w Structure of nanoscale materials
02.70.Dh Finite-element and Galerkin methods
68.65.La Quantum wires (patterned in quantum wells)

Enhanced coupling of light from organic light emitting diodes using nanoporous films

H. J. Peng, Y. L. Ho, X. J. Yu, and H. S. Kwok

J. Appl. Phys. 96, 1649 (2004); http://dx.doi.org/10.1063/1.1765859 (6 pages) | Cited 23 times

Online Publication Date: 26 July 2004

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We have demonstrated an approach to enhance the light extraction efficiency for organic light emitting diode (OLED). Nanoporous alumina film was used to modify the optical wave propagation and coupling of light from the OLED. Experimental results showed an increase of over 50% in the coupling efficiency of the nanoporous device, without affecting the electrical properties of the OLED. Effective medium theory can be used to model the optical properties of the nanoporous media and simulated the optical characteristics of the OLED successfully.
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85.60.Jb Light-emitting devices

Influence of process parameters on the morphology of Au∕SiO2 nanocomposites synthesized by radio-frequency sputtering

Davide Barreca, Alberto Gasparotto, Eugenio Tondello, Giovanni Bruno, and Maria Losurdo

J. Appl. Phys. 96, 1655 (2004); http://dx.doi.org/10.1063/1.1766083 (11 pages) | Cited 25 times

Online Publication Date: 26 July 2004

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Metal nanoparticles on oxide matrices have gained a markedly increasing consideration with regard to both scientific and applicative purposes, thanks to the possibility of tailoring the system characteristics by a proper choice of the preparation route and the processing conditions. In the present work, Au∕SiO2 nanocomposites were prepared by radio-frequency (rf) sputtering of gold from Ar plasmas on amorphous silica substrates. Particular attention was devoted to the influence of the synthesis parameters on the chemicophysical properties of the final nanosystems. To this regard, both in situ and ex situ characterization techniques were adopted. In particular, laser reflection interferometry was employed for an in situ monitoring of growth processes, while ex situ analyses were specifically dedicated to the investigation of Au∕SiO2 nanostructure, chemical composition, optical properties, and surface morphology (glancing-incidence x-ray diffraction, transmission electron microscopy, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, ultraviolet-visible absorption, and atomic force microscopy). The obtained results showed the possibility of tailoring the Au∕SiO2 morphology from clusterlike to islandlike systems or continuous films, with consequent modification of the optical properties, by a proper choice of total pressure, rf power, deposition time, and growth temperature.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
81.05.Mh Cermets, ceramic and refractory composites
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Jv Interfaces; heterostructures; nanostructures

Cobalt nanoparticles deposited and embedded in AlN: Magnetic, magneto-optical, and morphological properties

Y. Huttel, H. Gómez, C. Clavero, A. Cebollada, G. Armelles, E. Navarro, M. Ciria, L. Benito, J. I. Arnaudas, and A. J. Kellock

J. Appl. Phys. 96, 1666 (2004); http://dx.doi.org/10.1063/1.1767975 (8 pages) | Cited 14 times

Online Publication Date: 26 July 2004

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We present a structural, morphological, magnetic, and magneto-optical study of cobalt nanoparticles deposited on 50 math AlN∕c-sapphire substrates and embedded in an AlN matrix. The dependence of the properties of Co nanoclusters deposited on AlN with growth temperature and amount of deposited Co are studied and discussed. Also we directly compare the properties of as grown and AlN embedded Co nanoclusters and show that the AlN matrix has a strong impact on their magnetic and magneto-optical properties.
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78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Cd Deposition by sputtering
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
81.05.Bx Metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization

State of the metal core in nanosecond exploding wires and related phenomena

G. S. Sarkisov, P. V. Sasorov, K. W. Struve, and D. H. McDaniel

J. Appl. Phys. 96, 1674 (2004); http://dx.doi.org/10.1063/1.1767976 (13 pages) | Cited 19 times

Online Publication Date: 26 July 2004

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Experiments show that an expanding metal wire core that results from a nanosecond electrical explosion in vacuum consists primarily of three different states: solid, microdrop, and gas-plasma. The state of the wire core depends both on the amount of energy deposited before the voltage breakdown and on the heating conditions. For small amounts of deposited energy (on the order of solid-stage enthalpy), the wire core remains in a solid state or is partially disintegrated. For a high level of deposited energy (more than vaporization energy) the wire core is in a gas-plasma state. For an intermediate level of deposited energy (more than melting but less than vaporization), the wire disintegrates into hot liquid microdrops or clusters of submicron size. For a wire core in the cluster state, interferometry demonstrates weak (or even absent) phaseshift. Light emission shows a "firework effect"—the long late-time radiation related to the emission by the expanding cylinder of hot microparticles. For the wire core in a gas-plasma state, interferometry demonstrates a large phaseshift and a fast reduction in light emission due to adiabatic cooling of the expanding wire core. The simulation of this firework effect agrees well with experimental data, assuming submicron size and a temperature approaching boiling for the expanded microparticles cylinder.
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52.80.Qj Explosions; exploding wires
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