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28 Apr 2003

Volume 82, Issue 17, pp. 2749-2924

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 2957 (2003); http://dx.doi.org/10.1063/1.1571977 (3 pages)

Tadashi Kawazoe, Kiyoshi Kobayashi, Suguru Sangu, and Motoichi Ohtsu
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Spectral dependence of the squared average optical transition matrix element associated with hydrogenated amorphous silicon

Stephen Karrer O’Leary

Appl. Phys. Lett. 82, 2784 (2003); http://dx.doi.org/10.1063/1.1568148 (3 pages) | Cited 7 times

Online Publication Date: 21 April 2003

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Using an empirical model for the density of states functions, in conjunction with an elementary model for the optical transition matrix elements, the spectral dependence of the squared average optical transition matrix element associated with hydrogenated amorphous silicon was evaluated. It was predicted that this squared average matrix element saturates at and beyond the mobility gap, decreases sharply just below the mobility gap as the photon energy is diminished, and then saturates at sufficiently low photon energies. The value of the squared average optical transition matrix element at low photon energies depends on the density of localized electronic states. The results suggest that a careful experimental measurement of the spectral dependence of this matrix element will provide one with a direct means of determining the position of the mobility gap of this semiconductor. © 2003 American Institute of Physics.
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78.20.Bh Theory, models, and numerical simulation
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.23.An Theories and models; localized states
71.55.Jv Disordered structures; amorphous and glassy solids
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance

Indirect excitation of Er3+ in sol-gel hybrid films doped with an erbium complex

Oun-Ho Park, Se-Young Seo, Byeong-Soo Bae, and Jung H. Shin

Appl. Phys. Lett. 82, 2787 (2003); http://dx.doi.org/10.1063/1.1570919 (3 pages) | Cited 30 times

Online Publication Date: 21 April 2003

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Transparent sol-gel hybrid films doped with erbium tris 8-hydroxyquinoline were prepared using methyltriethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane as precursors. We obtain a strong 1.53-μm Er3+ luminescence with a wide full width at half-maximum and no thermal quenching. Comparison of absorption of the film with the pump wavelength dependence of Er3+ luminescence intensity indicates the presence of an efficient indirect excitation path for Er3+ via organic ligands. © 2003 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Sq Composite materials
78.55.-m Photoluminescence, properties and materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Excellent ultrasonic absorption ability of carbon-nanotube-reinforced bulk metallic glass composites

Zan Bian, Ru Ju Wang, De Qian Zhao, Ming Xiang Pan, Zhi Xin Wang, and Wei Hua Wang

Appl. Phys. Lett. 82, 2790 (2003); http://dx.doi.org/10.1063/1.1570938 (3 pages) | Cited 12 times

Online Publication Date: 21 April 2003

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Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass composites (BMGCs) containing carbon nanotubes (CNTs) are found to have a strong ultrasonic wave absorption ability. Ultrasonic attenuation coefficients of Zr-based BMGCs increase dramatically with increasing volume fraction of CNTs. The excellent ultrasonic wave absorption ability is attributed mainly to the multiscattering caused by the CNTs and ZrC phase dispersing randomly in the glass matrix. © 2003 American Institute of Physics.
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62.65.+k Acoustical properties of solids

Multiple temperature regimes of radiative decay in CdSe nanocrystal quantum dots: Intrinsic limits to the dark-exciton lifetime

S. A. Crooker, T. Barrick, J. A. Hollingsworth, and V. I. Klimov

Appl. Phys. Lett. 82, 2793 (2003); http://dx.doi.org/10.1063/1.1570923 (3 pages) | Cited 97 times

Online Publication Date: 21 April 2003

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We investigate the strongly temperature-dependent radiative lifetime of electron–hole excitations in colloidal CdSe nanocrystal quantum dots over nearly three orders of magnitude in temperature (300 K to 380 mK). These studies reveal an intrinsic, radiative upper limit of ∼1 μs for the storage of excitons below 2 K. At higher temperatures, exciton lifetimes are consistent with thermal activation from the dark-exciton ground state, but with two different activation thresholds. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
73.21.La Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)

Self-organized titanium oxide nanodot arrays by electrochemical anodization

Po-Lin Chen, Cheng-Tzu Kuo, Tzeng-Guang Tsai, Bo-Wei Wu, Chiung-Chih Hsu, and Fu-Ming Pan

Appl. Phys. Lett. 82, 2796 (2003); http://dx.doi.org/10.1063/1.1571661 (3 pages) | Cited 34 times

Online Publication Date: 21 April 2003

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Ordered nanodot arrays of titanium oxides were prepared from TiN/Al films on the silicon substrate by electrochemical anodization of a TiN layer using a nanoporous anodic aluminum oxide film as the template. The microstructure of the nanodot arrays was studied by transmission electron microscopy and scanning electron microscopy, and the chemical composition of nanodots was analyzed by electron energy loss spectroscopy. The as-prepared nanodots are basically composed of amorphous TiOx with a hexagonal arrangement and an average diameter of about 60 nm. Using this approach, it is expected that nanodot arrays of various oxide semiconductors can be achieved. © 2003 American Institute of Physics.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.65.Mq Oxidation
81.16.Dn Self-assembly
61.46.-w Structure of nanoscale materials
68.37.Lp Transmission electron microscopy (TEM)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.20.Uv Electron energy loss spectroscopy

Magneto-optical investigations of single self-assembled InAs/InGaAlAs quantum dashes

T. Mensing, L. Worschech, R. Schwertberger, J. P. Reithmaier, and A. Forchel

Appl. Phys. Lett. 82, 2799 (2003); http://dx.doi.org/10.1063/1.1570518 (3 pages) | Cited 9 times

Online Publication Date: 21 April 2003

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Small mesa structures with only a few self-assembled InAs dashes for optical studies were realized by electron-beam lithography and etching techniques. The heterostructure was grown by molecular-beam epitaxy lattice-matched to an InP substrate and consists of an In0.53Ga0.23Al0.24As layer embedding in the center 3.3 monolayers of InAs. By self-assembly InAs dashes were formed. At low temperatures, narrow emission lines associated with electron-hole pairs confined in single dashes are observed. Biexciton transitions with typical binding energies of about 3.5 meV are found. The diamagnetic shift and the Zeeman splitting of single excitons are studied in magnetic fields up to 8 T in Faraday configuration. A large variation of the exciton g factor with the emission energy of quantum dashes is observed. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
73.21.La Quantum dots
78.55.Cr III-V semiconductors
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Proton-implantation-induced photoluminescence enhancement in self-assembled InAs/GaAs quantum dots

Yalin Ji, Guibin Chen, Naiyun Tang, Qing Wang, X. G. Wang, J. Shao, X. S. Chen, and W. Lu

Appl. Phys. Lett. 82, 2802 (2003); http://dx.doi.org/10.1063/1.1568547 (3 pages) | Cited 7 times

Online Publication Date: 21 April 2003

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We have used proton-implantation-induced intermixing and a passivation effect to enhance the light-emission efficiency in multilayer InAs/GaAs quantum dots (QDs). Photoluminescence (PL) spectroscopy is used to study both the intermixing and passivation effects. Besides the blueshift of the luminescence peak due to the intermixing-induced energy band variation, a six times higher PL intensity increase is observed, relative to that of as-grown QDs, with a proton implantation dose of 5×1013 cm−2 followed by rapid thermal annealing at 700 °C. These effects are beneficial to both the quantum efficiency and the wavelength tuning of optoelectronic devices. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
61.80.Jh Ion radiation effects
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.35.Fx Diffusion; interface formation

Role of the host matrix in the carrier recombination of InGaAsN alloys

A. Vinattieri, D. Alderighi, M. Zamfirescu, M. Colocci, A. Polimeni, M. Capizzi, D. Gollub, M. Fischer, and A. Forchel

Appl. Phys. Lett. 82, 2805 (2003); http://dx.doi.org/10.1063/1.1569983 (3 pages) | Cited 9 times

Online Publication Date: 21 April 2003

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We present an experimental study of the carrier recombination dynamics in high-quality (InGa)(AsN)/GaAs and Ga(AsN)/GaAs quantum-well structures after picosecond excitation. A comparison among samples with and without nitrogen and with different In concentration shows that nonradiative channels originated in the host matrix [i.e., (InGa)As and GaAs] play a dominant role in the recombination dynamics of these heterostructures. © 2003 American Institute of Physics.
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73.63.Hs Quantum wells
81.07.St Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
73.21.Fg Quantum wells
78.47.-p Spectroscopy of solid state dynamics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Percolation-based vibrational picture to estimate nonrandom N substitution in GaAsN alloys

O. Pagès, T. Tite, D. Bormann, E. Tournié, O. Maksimov, and M. C. Tamargo

Appl. Phys. Lett. 82, 2808 (2003); http://dx.doi.org/10.1063/1.1566801 (3 pages) | Cited 15 times

Online Publication Date: 21 April 2003

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The number of N atoms in N-rich regions mostly due to nonrandom N incorporation in GaAsN (N∼4%), referred to as the Nr rate, is studied using a nonstandard Raman setup that addresses transverse symmetry. The Ga–N optical range shows a two-mode signal which discriminates between the N-poor (Np) and N-rich (Nr) regions. This is discussed via a percolation-based picture for Be-chalcogenide alloys, which exhibit mechanical contrast with regard to the shear modulus. This applies to GaAs–GaN even though the contrast is in the bulk modulus. The balance of Nr/Np strength provides a Nr rate of ∼30%, i.e., much larger than the corresponding Be rate of ∼4% in random Be-based alloys. © 2003 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
62.20.D- Elasticity
61.50.Lt Crystal binding; cohesive energy

Microscopic superelastic behavior of a nickel-titanium alloy under complex loading conditions

Wangyang Ni, Yang-Tse Cheng, and David S. Grummon

Appl. Phys. Lett. 82, 2811 (2003); http://dx.doi.org/10.1063/1.1569984 (3 pages) | Cited 22 times

Online Publication Date: 21 April 2003

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The microscopic superelastic behavior of a nickel-titanium (NiTi) alloy has been studied by instrumented indentation experiments using both spherical and pyramidal (e.g., Berkovich) diamond indenters. The indentation load–displacement curves for a superelastic NiTi and an annealed copper were obtained under a range of indentation conditions. We show that indentation-induced superelasticity exists under both spherical and pyramidal indenters, which may be exploited for many applications, ranging from microelectromechanical systems to surface engineering. © 2003 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
62.20.F- Deformation and plasticity
62.20.Qp Friction, tribology, and hardness
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