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27 Dec 2004

Volume 85, Issue 26, pp. 6323-6432

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 6409 (2004); http://dx.doi.org/10.1063/1.1839274 (3 pages)

Peter D. D. Schwindt, Svenja Knappe, Vishal Shah, Leo Hollberg, John Kitching, Li-Anne Liew, and John Moreland
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Effects of rapid thermal annealing on quality of In0.52Al0.48As∕In0.53Ga0.47As multiquantum wells grown on a compositionally graded InAlAs∕InAlGaAs metamorphic buffer layer

Soo-Ghang Ihn, Seong-June Jo, and Jong-In Song

Appl. Phys. Lett. 85, 6335 (2004); http://dx.doi.org/10.1063/1.1833566 (3 pages) | Cited 2 times

Online Publication Date: 17 December 2004

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We report improvement in crystalline quality of In0.52Al0.48As∕In0.53Ga0.47As multiquantum wells (MQWs) and compositionally graded InAlAs∕InAlGaAs metamorphic buffer grown on GaAs by using postgrowth rapid thermal annealing (RTA). Dependence of optical and structural properties of the MQWs on RTA was investigated by using photoluminescence (PL) and triple-axis x-ray diffraction measurements. After the RTA, the PL intensity of the MQWs increased, while the linewidth decreased. Also, the triple-axis contour maps of the MQWs showed increase in peak intensity of epilayers as well as crystalline reformation indicated by narrower mosaic spread and restoration of epilayer tilt to the substrate orientation.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
68.65.Fg Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.40.Tv Optical and dielectric properties related to treatment conditions

Epitaxial growth and surface modeling of ZnO on c-plane Al2O3

T. E. Murphy, S. Walavalkar, and J. D. Phillips

Appl. Phys. Lett. 85, 6338 (2004); http://dx.doi.org/10.1063/1.1842357 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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The growth of ZnO on c-plane sapphire by molecular beam epitaxy is presented for varying ratios of zinc and oxygen flux. Reflection high energy electron diffraction patterns during epitaxial growth suggest clear differences in the evolution of surface morphology for differing Zn flux. Atomic force microscope images indicate sizable hexagonal features in the surface morphology for Zn-rich material. A stochastic growth model is presented to represent the experimental ZnO surface, where differences in adatom lateral diffusion length are suspected to be the cause of the differing surface morphology.
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81.05.Dz II-VI semiconductors
81.15.Aa Theory and models of film growth
66.30.Dn Theory of diffusion and ionic conduction in solids
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ps Atomic force microscopy (AFM)

Near-field second-harmonic imaging of thin ferromagnetic films

W. Dickson, S. Takahashi, R. Pollard, and A. V. Zayats

Appl. Phys. Lett. 85, 6341 (2004); http://dx.doi.org/10.1063/1.1842369 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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The principles of magnetic domain image formation in second-harmonic near-field microscopy have been investigated in the case of in-plane magnetic anisotropy. Due to the electromagnetic interaction between a probe and a surface, magnetic contrast can be achieved by observing near-field intensity variations of the SH light for both polarizations of the fundamental light in the longitudinal and transverse illumination configurations without polarization analysis. Domains in thin ferromagnetic films of Ni and Co exhibiting in-plane magnetization have been imaged using the developed approach.
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75.50.Cc Other ferromagnetic metals and alloys
68.55.-a Thin film structure and morphology
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.37.Uv Near-field scanning microscopy and spectroscopy
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects

Charge controlled, fixed optic axis analog (“v-shaped”) switching of a bent-core ferroelectric liquid crystal

Michael J. O’Callaghan, Michael D. Wand, Christopher M. Walker, and Michi Nakata

Appl. Phys. Lett. 85, 6344 (2004); http://dx.doi.org/10.1063/1.1842372 (3 pages) | Cited 11 times

Online Publication Date: 17 December 2004

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Recently discovered anticlinic ferroelectric liquid crystals (FLCs) offer a mode of fast fixed-optic-axis electro-optic modulation useful for a variety of applications. In addition, the high spontaneous polarization of a member of this class of FLCs (∼500–600 nC∕cm2) suggests that it is a good candidate for electrostatically controlled thresholdless analog switching, whereas conventional SmC* FLCs have a binary response. Using a simple charge control drive circuit, we have found that this FLC is in fact capable of hysteresis-free analog switching. An optical model suggests that this class of FLCs might be engineered to have a much larger electro-optic effect than seen in this example.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
78.20.Jq Electro-optical effects
77.80.Dj Domain structure; hysteresis
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Evaluation of optical quality and defect properties of GaNxP1−x alloys lattice matched to Si

M. Izadifard, J. P. Bergman, I. Vorona, W. M. Chen, I. A. Buyanova, A. Utsumi, Y. Furukawa, S. Moon, A. Wakahara, and H. Yonezu

Appl. Phys. Lett. 85, 6347 (2004); http://dx.doi.org/10.1063/1.1839286 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2004

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By using a variety of optical characterization techniques, including cathodoluminescence, temperature-dependent cw- and time-resolved photoluminescence (PL), and PL excitation spectroscopies, high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates is demonstrated and is shown to be comparable to that of the “state-of-the-art” GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitial atoms (Gai).
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78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology

Time-resolved photoluminescence in Mobil Composition of Matter-48

Y. L. Liu, W. Z. Lee, J. L. Shen, Y. C. Lee, P. W. Cheng, and C. F. Cheng

Appl. Phys. Lett. 85, 6350 (2004); http://dx.doi.org/10.1063/1.1842351 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2004

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Dynamical properties of Mobil Composition of Matter (MCM)-48 were studied by time-resolved photoluminescence (PL). The PL intensity exhibits a clear nonexponential profile, which can be fitted by a stretched exponential function. In the temperature range from 50 to 300 K, the PL decay lifetime becomes thermally activated by a characteristic energy of 25 meV, which is suggested to be an indication of the phonon-assisted nonradiative process. A model is proposed to explain the relaxation behavior of the PL in MCM-48.
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78.55.Mb Porous materials
78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics

In situ formation of two amorphous phases by liquid phase separation in Y–Ti–Al–Co alloy

B. J. Park, H. J. Chang, D. H. Kim, and W. T. Kim

Appl. Phys. Lett. 85, 6353 (2004); http://dx.doi.org/10.1063/1.1842360 (3 pages) | Cited 66 times

Online Publication Date: 17 December 2004

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The Y28Ti28Al24Co20 alloy undergoes metastable liquid phase separation in the under-cooled liquid state and subsequently solidifies into two different Y-rich and Ti-rich amorphous phases. Secondary phase separation occurs due to the supersaturation of the primary separated liquids as the temperature decreases. Depending on the degree of local undercooling, a wide range of length scale of the microstructure is observed. The characteristic length scale of the two amorphous phases is ∼250 nm near the air side of the ribbon, and ∼25 nm near the wheel side of the ribbon.
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81.05.Kf Glasses (including metallic glasses)
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses
64.60.My Metastable phases
64.75.-g Phase equilibria
81.30.Fb Solidification
64.70.D- Solid-liquid transitions

Ce3+-doped fibers for remote radiation dosimetry

A. Vedda, N. Chiodini, D. Di Martino, M. Fasoli, S. Keffer, A. Lauria, M. Martini, F. Moretti, G. Spinolo, M. Nikl, N. Solovieva, and G. Brambilla

Appl. Phys. Lett. 85, 6356 (2004); http://dx.doi.org/10.1063/1.1840127 (3 pages) | Cited 17 times

Online Publication Date: 17 December 2004

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A radioluminescent (RL) dosimetric system, based on a SiO2 optical fiber with the core doped by Ce3+ ions as luminescent activators has been investigated. Structural and optical properties of the luminescent fiber have been studied by Raman, refractive index, RL and scintillation time decay measurements, and compared to those obtained on bulk material. The RL response of a composite fiber made of a short portion of active Ce-doped fiber coupled to a long commercial one has been investigated by x-ray irradiation. A linear RL intensity response has been found in the dose rate interval 6×10−3–40 mGy∕s together with a good radiation hardness, suggesting possible application in low-dose monitoring.
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42.70.Ce Glasses, quartz
42.81.Cn Fiber testing and measurement of fiber parameters
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Qr Amorphous materials; glasses and other disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.80.Cb X-ray effects
61.82.Ms Insulators

Composition measurement in strained AlGaN epitaxial layers using x-ray diffraction

D. J. Wallis, A. M. Keir, R. S. Balmer, D. E. J. Soley, and T. Martin

Appl. Phys. Lett. 85, 6359 (2004); http://dx.doi.org/10.1063/1.1835999 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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An x-ray diffraction technique is described which, by careful choice of the x-ray reflection used, minimizes errors in composition measurements resulting from strain and uncertainties in the elastic constants of a material. The method is applied to the AlGaN system, which shows a wide range of values for Poisson’s ratio in the literature and significant variation in strain state due to the high dislocation content and large thermal expansion mismatch with the substrate. It is demonstrated that accurate composition measurements of partially relaxed AlxGa1−xN layers (x<0.3) with thickness >20 nm can be made from a single measurement.
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81.05.Ea III-V semiconductors
68.55.Nq Composition and phase identification
68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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