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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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Three-level picture for chirp-dependent fluorescence yields under femtosecond optical pulse irradiation

Naoyuki T. Hashimoto, Kazuhiko Misawa, and Roy Lang

Appl. Phys. Lett. 82, 2749 (2003); http://dx.doi.org/10.1063/1.1571225 (3 pages) | Cited 4 times

Online Publication Date: 21 April 2003

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We propose a simple model to account for chirp-dependent fluorescence yields from a substance under femtosecond optical pulse irradiation. The model is simple, consisting of a three-level system, and yet it explains the essential feature of the chirp-dependent fluorescence yields experimentally observed, for example, with cyanine dye molecules. Based on the model, the dependence of the fluorescence on the excitation pulse properties such as the chirp rate and pulse intensity has been examined in detail. The results indicate that chirp-dependent fluorescence can be utilized as a convenient means for characterizing phase distortions in optical pulses such as those in optical fiber communication systems. © 2003 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.50.-p Quantum optics
78.55.-m Photoluminescence, properties and materials

Multimode combined intense laser-induced electron acceleration and violent bunch compression

P. X. Wang, Ch. X. Tang, and Sh. J. Huang

Appl. Phys. Lett. 82, 2752 (2003); http://dx.doi.org/10.1063/1.1569417 (3 pages) | Cited 6 times

Online Publication Date: 21 April 2003

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The ponderomotive potential structure of a multimode combined intense laser beam is studied. Using a three-dimensional test particle simulation, the interaction of slow electrons with the combined laser beam in vacuum is investigated. The calculation shows that electrons distributed on a large scale can be accelerated to relativistic energy in vacuum. A violent longitudinal bunch compression phenomenon is also presented and discussed. © 2003 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Ah General laser theory
41.60.Cr Free-electron lasers

Carrier leakage in InGaN quantum well light-emitting diodes emitting at 480 nm

I. A. Pope, P. M. Smowton, P. Blood, J. D. Thomson, M. J. Kappers, and C. J. Humphreys

Appl. Phys. Lett. 82, 2755 (2003); http://dx.doi.org/10.1063/1.1570515 (3 pages) | Cited 55 times

Online Publication Date: 21 April 2003

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Pulsed light–current characteristics of InGaN/GaN quantum well light-emitting diodes have been measured as a function of temperature, with sublinear behavior observed over the whole temperature range, 130–330 K. A distinctive temperature dependence is also noted where the light output, at a fixed current, initially increases with temperature, before reaching a maximum at 250 K and then decreases with subsequent increases in temperature. On the basis of a drift diffusion model, we can explain the sublinear light–current characteristics and the temperature dependence by the influence of the large acceptor ionization energy in Mg-doped GaN together with a triangular density of states function characteristic of localized states. Without the incorporation of localization effects, we are unable to reproduce the temperature dependence whilst maintaining emission at the observed wavelength. This highlights the importance of localization effects on device performance. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.Fg Quantum wells
78.67.De Quantum wells
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.20.Fz Weak or Anderson localization

Multiphoton fabrication of periodic structures by multibeam interference of femtosecond pulses

Toshiaki Kondo, Shigeki Matsuo, Saulius Juodkazis, Vygantas Mizeikis, and Hiroaki Misawa

Appl. Phys. Lett. 82, 2758 (2003); http://dx.doi.org/10.1063/1.1569987 (3 pages) | Cited 49 times

Online Publication Date: 21 April 2003

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Femtosecond laser pulses are useful for laser microfabrication through multiphoton absorption. However, it is difficult to create interference of femtosecond pulses for the fabrication of periodic structures. In this letter, we report the fabrication of two-dimensional periodic structures by means of multibeam interference of femtosecond pulses. Scanning electron microscopy revealed a rod structure arranged into a square lattice. The possibility of controlling the period of the lattice, rod thickness, and rod shape were demonstrated. © 2003 American Institute of Physics.
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42.62.Cf Industrial applications
81.20.Wk Machining, milling
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Increasing shear force microscopy scanning rate using active quality-factor control

M. Antognozzi, M. D. Szczelkun, A. D. L. Humphris, and M. J. Miles

Appl. Phys. Lett. 82, 2761 (2003); http://dx.doi.org/10.1063/1.1571233 (3 pages) | Cited 13 times

Online Publication Date: 21 April 2003

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The use of an active quality-factor control device has been demonstrated to increase the scanning rate of a shear force microscope by lowering the quality factor of the oscillating probe. Shear force microscopy (often used in combination with scanning near-field optical microscopy) requires slow scanning rates due to the long (>1 ms) time constant of the oscillating element (optical fiber or tuning fork). By electronically reducing the quality factor of the probe, it was possible to tune the time constant and correspondingly reduce the overall scanning time by a factor of 4. It was also seen that probes with high quality factors could manifest an unstable behavior; by reducing the quality factor of the probe, it was possible to increase the signal-to-noise ratio and so improve the imaging resolution. Deoxyribonucleic acid molecules deposited onto mica and imaged in air were used to demonstrate the technique. © 2003 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
87.64.Dz Scanning tunneling and atomic force microscopy
87.14.G- Nucleic acids

Efficient blue light-emitting diodes with InGaN/GaN triangular shaped multiple quantum wells

R. J. Choi, Y. B. Hahn, H. W. Shim, M. S. Han, E. K. Suh, and H. J. Lee

Appl. Phys. Lett. 82, 2764 (2003); http://dx.doi.org/10.1063/1.1570511 (3 pages) | Cited 9 times

Online Publication Date: 21 April 2003

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InGaN/GaN triangular shaped multiple quantum wells (QWs) grown by grading In composition with time were adopted as an active layer of blue light-emitting diodes (LEDs). Compared to the LEDs with conventional rectangular QW structures, the triangular QW LEDs showed a higher intensity and a narrower linewidth of electrical luminescence (EL), a lower operation voltage, and a stronger light-output power. EL spectra of the triangular-QW-based LEDs also showed that the peak energy is nearly independent of the injection current and temperature, indicating that the triangular QW LED is more efficient and stable than the rectangular one. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.60.Fi Electroluminescence

Tunable photonic crystals fabricated in III-V semiconductor slab waveguides using infiltrated liquid crystals

Ch. Schuller, F. Klopf, J. P. Reithmaier, M. Kamp, and A. Forchel

Appl. Phys. Lett. 82, 2767 (2003); http://dx.doi.org/10.1063/1.1570921 (3 pages) | Cited 56 times

Online Publication Date: 21 April 2003

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Microcavity structures formed by two-dimensional photonic crystal mirrors with triangular lattice and a crystal period of 280 nm suitable for transmission experiments at about 1 μm were fabricated in III-V semiconductor planar waveguides. The photonic crystals were filled with a liquid crystal of type E7. The wavelength of the resonance peak can be shifted by the temperature-dependent refractive index of the liquid crystal. The temperature shift follows the typical refractive index behavior of liquid crystals, with a jump in wavelength at the clearing point (about 60 °C) and a continuous shift below. The wavelength jump is about 4 nm within a few Kelvin, while the total shift amounts to 9 nm between 20 and 70 °C. The experimental results agree well with the calculated temperature dependent photonic band structure by assuming a preferential alignment of the liquid-crystal molecules parallel to the holes. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.70.Df Liquid crystals
42.65.Wi Nonlinear waveguides
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

GaAs-based near-infrared omnidirectional reflector

Yeonsang Park, Young-Geun Roh, Chi-O Cho, Heonsu Jeon, Min Gyu Sung, and J. C. Woo

Appl. Phys. Lett. 82, 2770 (2003); http://dx.doi.org/10.1063/1.1569045 (3 pages) | Cited 19 times

Online Publication Date: 21 April 2003

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We introduce a compound-semiconductor-based omnidirectional reflector. A four-layer-pair stack of GaAs/AlAs was grown epitaxially using molecular-beam epitaxy, and was then converted to a GaAs/Al2O3 multilayer stack by selective oxidation of the AlAs layers. The resultant one-dimensional photonic crystal exhibited omnidirectional reflection properties in near-IR wavelength range below 1 μm. Reflectance spectra measured at various incidence angles and polarizations were observed to be in good agreement with theoretically simulated results. © 2003 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.79.Wc Optical coatings
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.Qs Photonic bandgap materials
78.30.Fs III-V and II-VI semiconductors
81.65.Mq Oxidation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Semiconductor mirror for dynamic dispersion compensation

A. Isomäki, A. Vainionpää, J. Lyytikäinen, and O. G. Okhotnikov

Appl. Phys. Lett. 82, 2773 (2003); http://dx.doi.org/10.1063/1.1569990 (2 pages) | Cited 3 times

Online Publication Date: 21 April 2003

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We report on a monolithic Gires–Tournois semiconductor interferometer used to generate a tunable delay. Controllable saturable absorption in optically pumped multiple-quantum-well semiconductor reflector was shown to provide promising means for rapid changing the group delay of the reflector, and represents an attractive form of dynamic dispersion compensation. © 2003 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
78.67.De Quantum wells
81.07.St Quantum wells
07.60.Ly Interferometers
81.05.Ea III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.82.Gw Other integrated-optical elements and systems
42.65.-k Nonlinear optics

Lens-free heterodyne detection for transient grating experiments

K. Katayama, M. Yamaguchi, and T. Sawada

Appl. Phys. Lett. 82, 2775 (2003); http://dx.doi.org/10.1063/1.1569051 (3 pages) | Cited 28 times

Online Publication Date: 21 April 2003

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An enhanced technique of heterodyne detection for transient grating experiments has been developed. This technique features a very simple optical alignment because no lenses are used to focus beams on the samples. It was applied to a vapor-deposited gold thin film (thickness: 30 nm), and the detected signal was confirmed to consist of a heterodyne component based on the dependence of the signal intensity on the pump intensity. Furthermore, this technique was shown to provide easy control of the phase difference between the probe and reference beams. © 2003 American Institute of Physics.
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42.79.Dj Gratings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Tuning of the blue emission from europium-doped alkaline earth chloroborate thin films activated in air

Jianhua Hao, J. Gao, and Michael Cocivera

Appl. Phys. Lett. 82, 2778 (2003); http://dx.doi.org/10.1063/1.1569048 (3 pages) | Cited 14 times

Online Publication Date: 21 April 2003

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Thin films of M2B5O9Cl:Eu (M = Ca, Sr, Ba) were prepared on glass substrates using spray pyrolysis. Blue cathodoluminescence due to the abnormal reduction of Eu3+→Eu2+ was obtained by annealing films in air. The cation of the host lattice was found to affect the effectiveness of the reduction process, which could result in influencing the emission band. By selecting types and composition of alkaline cation, it was possible to tune the dominant emitting wavelength between 435 to 465 nm. Activation of the films occurred at temperatures suitable for the use of glass substrates. © 2003 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
68.55.Nq Composition and phase identification
71.55.Ht Other nonmetals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Tv Optical and dielectric properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
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Flat triode structure with a pulsed coplanar discharge channel representing similar features to a field-effect transistor

Osamu Sakai, Satoshi Hashimoto, and Akitsugu Hatano

Appl. Phys. Lett. 82, 2781 (2003); http://dx.doi.org/10.1063/1.1570510 (3 pages) | Cited 5 times

Online Publication Date: 21 April 2003

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A completely flat configuration of three electrodes generates a regulated coplanar discharge in a pulse operation. The discharge current, flowing between one pair of electrodes, is monotonously controlled by the third electrode which keeps its isolation without any insulator layer. Current regulation mechanism is revealed by experimental and numerical analyses, which indicate that such a feature results from the mixed effects of electrode separation distance, gas pressure, and distortion of a three-dimensional potential profile. © 2003 American Institute of Physics.
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84.47.+w Vacuum tubes
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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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p-type conductivity in wide-band-gap BaCuQF (Q = S,Se)

Hiroshi Yanagi, Janet Tate, Sangmoon Park, Cheol-Hee Park, and Douglas A. Keszler

Appl. Phys. Lett. 82, 2814 (2003); http://dx.doi.org/10.1063/1.1571224 (3 pages) | Cited 18 times

Online Publication Date: 21 April 2003

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BaCuQF (Q = S,Se) materials, candidate transparent p-type conductors, were prepared by solid-state reaction, and their bulk electrical and optical properties were evaluated. The room-temperature Seebeck coefficient and electrical conductivity of undoped BaCuQF pellets were +56 μV/K and 0.088 S/cm, respectively, for the sulfide fluoride, and +32 μV/K and 0.061 S/cm, respectively, for the selenide fluoride. The conductivity was greatly enhanced by the substitution of several percent of K for Ba; the highest conductivities were 82 S/cm for Ba0.9K0.1CuSF and 43 S/cm for Ba0.9K0.1SeF. The band gaps for Q = S and Q = Se were measured to be 3.2 and 3.0 eV, respectively. Undoped BaCuSF exhibits strong red luminescence near 630 nm under ultraviolet excitation. © 2003 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Pa Thermoelectric and thermomagnetic effects
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Investigation of degradation for ohmic performance of oxidized Au/Ni/Mg-doped GaN

Yow-Jon Lin, Zhen-Dao Li, Chou-Wei Hsu, Feng-Tso Chien, Ching-Ting Lee, Sheng-Tien Shao, and Hsing-Cheng Chang

Appl. Phys. Lett. 82, 2817 (2003); http://dx.doi.org/10.1063/1.1569991 (3 pages) | Cited 11 times

Online Publication Date: 21 April 2003

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The mechanism of ohmic contact degradation for the oxidized Au/Ni/Mg-doped GaN under various annealing times has been investigated. According to the results from x-ray photoelectron spectroscopy and the Cserveny’s concept, we found that an increase of hole concentration of NiOx would lead to the increasing barrier height and the increasing specific contact resistance (ρc) of oxidized Au/Ni/Mg-doped GaN. This suggests that the NiOx plays an important role in increasing (or reducing) the ρc of oxidized Au/Ni/Mg-doped GaN. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.61.Ey III-V semiconductors
73.40.Cg Contact resistance, contact potential
81.65.Mq Oxidation
61.72.Cc Kinetics of defect formation and annealing

Field-induced relaxation of bulk composition due to internal boundaries

J. Jamnik, X. Guo, and J. Maier

Appl. Phys. Lett. 82, 2820 (2003); http://dx.doi.org/10.1063/1.1570513 (3 pages) | Cited 12 times

Online Publication Date: 21 April 2003

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The establishment of compositional variations in solids caused by an external electric field usually requires electrodes that block either electronic or ionic charge carriers. Here we present unambiguous experimental and theoretical evidence that the compositional variations can occur even in the case of completely nonblocking electrodes if grain boundaries are present. In addition to the proper grain boundary impedance arc characterized by the dielectric relaxation time, τ, a second arc occurs at much lower frequencies (τδ). It is shown that this low-frequency response refers to a chemical relaxation (Warburg diffusion) induced by the selectively blocking grain boundary. The effect is the analogue to the chemical relaxation induced by selectively blocking electrodes (cf. Wagner–Hebb polarization).© 2003 American Institute of Physics.
Show PACS
72.60.+g Mixed conductivity and conductivity transitions
61.72.Mm Grain and twin boundaries
77.22.Gm Dielectric loss and relaxation
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