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23 Dec 2002

Volume 81, Issue 26, pp. 4895-5074

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Evidence of local and global scaling regimes in thin films deposited by sputtering: An atomic force microscopy and electrochemical study

Tersio G. Souza Cruz, M. U. Kleinke, and A. Gorenstein

Appl. Phys. Lett. 81, 4922 (2002); http://dx.doi.org/10.1063/1.1530739 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2002

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The surface morphology of NiOx thin films deposited by rf sputtering was studied by atomic force microscopy and by cyclic voltammetry. Linear relationships were observed in log–log plots of the interface width versus window length and in log–log plots of the peak current versus scan rate. Two different slopes were observed, by both techniques, indicating that distinct growth dynamics present in the system can be measured in different ways. Moreover, the calculated fractal dimensions are in excellent agreement: the local scaling regime corresponds to high scan rates and the global scaling regime corresponds to low scan rates, in accordance with the expected behavior for diffusion fronts. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)
81.15.Cd Deposition by sputtering

Optical study of the full photonic band gap in silicon inverse opals

E. Palacios-Lidón, A. Blanco, M. Ibisate, F. Meseguer, C. López, and J. Sánchez-Dehesa

Appl. Phys. Lett. 81, 4925 (2002); http://dx.doi.org/10.1063/1.1530752 (3 pages) | Cited 25 times

Online Publication Date: 17 December 2002

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An optical study of the band structure of both silicon–silica composite and silicon inverse opals is presented. The study is aimed at demonstrating the development of a full photonic band gap for a system already revealed as paradigmatic. The characterization is based on the comparison between the band structure calculations and optical reflectance spectroscopy experiments. This study is carried out for various symmetry points in the Brillouin zone, some never explored before as K, (110) and W, (210). The results show that, in accordance with the band structure, there is a certain frequency range that produces a reflectance peak regardless of orientation and can be assigned to the band gap. Similarly all other reflectance peaks can be accounted for by other band structure features. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.50.-p Quantum optics

Determination of the azimuthal orientational spread of GaN films by x-ray diffraction

Yue Jun Sun, Oliver Brandt, Tian Yu Liu, Achim Trampert, Klaus H. Ploog, Jürgen Bläsing, and Alois Krost

Appl. Phys. Lett. 81, 4928 (2002); http://dx.doi.org/10.1063/1.1531832 (3 pages) | Cited 33 times

Online Publication Date: 17 December 2002

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We present a simple but reliable method to determine the azimuthal orientational spread of imperfect epitaxial layers by x-ray diffraction. This method requires the measurement of ω-scans in skew geometry from reflections with increasing lattice plane inclination φ, and a fit of the data by a geometrical model that considers the simultaneous presence of polar and azimuthal orientational spread within the layer. The values thus obtained for various GaN layers grown on SiC are shown to be in good agreement with those measured directly by ϕ-scans of the (1math00) reflection in grazing incidence, and with those deduced from the edge dislocation densities determined by plan-view transmission electron microscopy. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.72.Lk Linear defects: dislocations, disclinations
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Magnetically-modulated refractive index of magnetic fluid films

S. Y. Yang, Y. F. Chen, H. E. Horng, Chin-Yih Hong, W. S. Tse, and H. C. Yang

Appl. Phys. Lett. 81, 4931 (2002); http://dx.doi.org/10.1063/1.1531831 (3 pages) | Cited 35 times

Online Publication Date: 17 December 2002

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We developed a setup to probe the refractive index of the magnetic fluid films under external magnetic fields. This setup possesses a high resolution of 0.0001 in the measured refractive index. It was found that the refractive index of the magnetic fluid depends linearly on the concentration of the dilute magnetic fluid under zero field. For a given magnetic fluid film, the refractive index increases with the increasing field strength over a critical value, and then becomes saturated as the field reaches around 200 Oe. It is noteworthy that the magnetically modulated refractive index of the magnetic fluid films could have great potential in electro-optical applications. © 2002 American Institute of Physics.
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75.50.Mm Magnetic liquids
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.60.Hv Refractometers and reflectometers

Optical characteristics of hexagonal GaN self-assembled quantum dots: Strong influence of built-in electric field and carrier localization

Yong-Hoon Cho, B. J. Kwon, J. Barjon, J. Brault, B. Daudin, H. Mariette, and Le Si Dang

Appl. Phys. Lett. 81, 4934 (2002); http://dx.doi.org/10.1063/1.1530375 (3 pages) | Cited 11 times

Online Publication Date: 17 December 2002

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Optical characteristics of hexagonal GaN self-assembled quantum dots (QDs) were systematically studied by photoluminescence (PL), PL excitation (PLE), time-resolved PL, and cathodoluminescence (CL). We observed a Stokes-like shift between PLE absorption edge and PL emission from the GaN QDs as well as from the Al(Ga)N base layer. With decreasing emission energy, the measured lifetime of the hexagonal GaN QDs emission increased, while that of the cubic GaN QDs kept almost constant. The optical emission from the GaN QDs was measured as a function of temperature from 10 to 300 K, and their properties were compared with GaN quantum-well structures. With increasing temperature, the PL intensity of Al(Ga)N base layer or GaN quantum wells was dramatically decreased, while that of GaN QDs was not changed much. We observed CL images showing strong carrier localization in GaN QDs. Therefore, we conclude that the GaN QD emissions are strongly influenced by built-in electric field as well as by carrier localization in the QDs. © 2002 American Institute of Physics.
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78.67.Hc Quantum dots
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Cr III-V semiconductors
73.63.Kv Quantum dots

Lasing from a single-quantum wire

Yuhei Hayamizu, Masahiro Yoshita, Shinichi Watanabe, Hidefumi Akiyama, Loren N. Pfeiffer, and Ken W. West

Appl. Phys. Lett. 81, 4937 (2002); http://dx.doi.org/10.1063/1.1532111 (3 pages) | Cited 32 times

Online Publication Date: 17 December 2002

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A laser with an active volume consisting of only a single-quantum wire in the one-dimensional (1D) ground state is demonstrated. The single wire is formed quantum mechanically at the T-shaped intersection of a 14 nm Al0.07Ga0.93As quantum well and a 6 nm GaAs quantum well, and is embedded in a 1D single-mode optical waveguide. We observe single-mode lasing from the quantum-wire ground state by optical pumping. The laser operates from 5 to 60 K, and has a low threshold pumping power of 5 mW at 5 K. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.Vb Quantum wires

Spinodal patterning in organic–inorganic hybrid layer systems

M. Müller-Wiegand, G. Georgiev, E. Oesterschulze, T. Fuhrmann, and J. Salbeck

Appl. Phys. Lett. 81, 4940 (2002); http://dx.doi.org/10.1063/1.1531223 (3 pages) | Cited 9 times

Online Publication Date: 17 December 2002

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We demonstrate a general feature of organic films between a substrate and a deformable cladding layer: the capability of forming periodic structures by heating above the glass transition temperature of the organic film. This patterning process by self-organization is caused by the interplay of dispersion interactions and mechanical stress which leads to spinodal deformation. The dynamic evolution of the structures was investigated by time-resolved light diffraction. By prepatterning the substrate, the direction of the waves can be controlled. © 2002 American Institute of Physics.
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68.65.Ac Multilayers
42.79.Wc Optical coatings

Giant polarized photoluminescence and photoconductivity in type-II GaAs/GaAsSb multiple quantum wells induced by interface chemical bonds

Y. S. Chiu, M. H. Ya, W. S. Su, T. T. Chen, Y. F. Chen, and H. H. Lin

Appl. Phys. Lett. 81, 4943 (2002); http://dx.doi.org/10.1063/1.1532108 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2002

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Anisotropic property of type-II GaAs/GaAsSb heterostructures was studied by photoluminescence (PL) and photoconductivity (PC). It was found that the PL and PC spectra exhibit a strong in-plane polarization with respect to 〈011〉 axis with polarization degrees up to 40%. We showed that the polarization does not depend on the excitation intensity as well as temperature, which excludes any extrinsic mechanisms related to the in-plane anisotropy. The observed polarized optical properties of GaAsSb/GaAs multiple quantum wells was attributed to the intrinsic property of the orientation of chemical bonds at heterointerfaces. © 2002 American Institute of Physics.
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78.67.De Quantum wells
81.07.St Quantum wells
68.65.Fg Quantum wells
72.40.+w Photoconduction and photovoltaic effects
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
73.63.Hs Quantum wells
73.21.Fg Quantum wells
61.50.Lt Crystal binding; cohesive energy
68.35.Ct Interface structure and roughness

Surface domain engineering in congruent lithium niobate single crystals: A route to submicron periodic poling

A. C. Busacca, C. L. Sones, V. Apostolopoulos, R. W. Eason, and S. Mailis

Appl. Phys. Lett. 81, 4946 (2002); http://dx.doi.org/10.1063/1.1532773 (3 pages) | Cited 25 times

Online Publication Date: 17 December 2002

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We describe a technique for surface domain engineering in congruent lithium niobate single crystals. The method is based on conventional electric-field poling, but involves an intentional overpoling step that inverts all the material apart from a thin surface region directly below the patterned photoresist. The surface poled structures show good domain uniformity, and the technique has so far been applied to produce domain periods as small as ∼1 μm. The technique is fully compatible with nonlinear optical integrated devices based on waveguide structures. © 2002 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
77.22.Ej Polarization and depolarization
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.82.Et Waveguides, couplers, and arrays

A neutron reflectometry study of the interface between poly(9,9-dioctylfluorene) and poly(methyl methacrylate)

A. M. Higgins, P. C. Jukes, S. J. Martin, M. Geoghegan, R. A. L. Jones, and R. Cubitt

Appl. Phys. Lett. 81, 4949 (2002); http://dx.doi.org/10.1063/1.1532531 (3 pages) | Cited 7 times

Online Publication Date: 17 December 2002

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Neutron reflectivity was used to study the interface between the semiconducting polymer poly(9,9-dioctylfluorene) (PFO) and the insulating polymer poly(methyl methacrylate) (PMMA). The PFO/PMMA interfacial width was measured in the nematic and crystalline phases of the PFO, both with the PMMA on top of the PFO and vice versa. These interfaces are broad compared to atomic length scales, with measured interfacial widths in the range from 10 to 20 Å. We found that the interfacial width was independent of both the chosen geometry and the thermal processing history. The equilibrium interfacial width only depended on temperature, with the width in the nematic phase of the PFO being broader than in the crystalline regime. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.41.+e Polymers, elastomers, and plastics
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