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24 Jul 2000

Volume 77, Issue 4, pp. 463-603

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AlAs/GaAs quantum cascade lasers based on large direct conduction band discontinuity

Cyrille Becker, Carlo Sirtori, Hideaki Page, Geneviève Glastre, Valentin Ortiz, Xavier Marcadet, Max Stellmacher, and Julien Nagle

Appl. Phys. Lett. 77, 463 (2000); http://dx.doi.org/10.1063/1.127059 (3 pages) | Cited 29 times

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The design and operation of quantum cascade (QC) lasers using AlAs/GaAs coupled quantum wells are reported. In this material system, the conduction band offset at the Γ point (∼1 eV) is much higher than in previously reported QC lasers. The use of high band discontinuity allows us to increase the energy separation among the subbands, thus suppressing thermally activated processes which limit device performance at high temperature. The measured thermal characteristics of these promising devices are strongly improved from previously reported GaAs-based QC lasers: The temperature dependence of the threshold current density is described by a very large T0 (320 K) and the laser slope efficiency does not vary for increasing heat sink temperatures. The maximum operating temperature is 230 K, limited by negative differential resistance effects that occur when the applied bias reaches 8 V. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Fq High-field and nonlinear effects

Discrete energy level separation and the threshold temperature dependence of quantum dot lasers

Oleg B. Shchekin, Gyoungwon Park, Diana L. Huffaker, and Dennis G. Deppe

Appl. Phys. Lett. 77, 466 (2000); http://dx.doi.org/10.1063/1.127012 (3 pages) | Cited 68 times

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Data are presented on one- and two-stack InAs quantum dot lasers that have reduced temperature sensitivity of their lasing threshold. Adjustment of dot size and composition is used to increase the energy separation between the ground and first excited radiative transition energies to 104 meV, with a dot density of ∼ 3.1×1010 cm−2. The one- and two-stack lasers show broad area as-cleaved room temperature threshold current densities as low as 43 and 35 A/cm2, respectively. The wide energy separation between the ground and first excited radiative transitions leads to significant improvements in the temperature sensitivity of threshold. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

High-repetition-rate, all-solid-state, Ti:sapphire-pumped optical parametric oscillator for the mid-infrared

P. J. Phillips, S. Das, and M. Ebrahimzadeh

Appl. Phys. Lett. 77, 469 (2000); http://dx.doi.org/10.1063/1.127013 (3 pages) | Cited 7 times

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We report a low-pump-threshold, all-solid-state subpicosecond optical parametric oscillator (OPO) for the mid-infrared based on periodically poled LiNbO3 and synchronously pumped by a mode-locked Ti:sapphire laser. Using a semimonolithic cavity design and hemispherical focusing, pump power thresholds of 17 mW and mid-infrared idler powers of 64 mW have been obtained in the 3.9–6 μm spectral range in a simple, practical, and compact configuration at pulse repetition rates of up to 322 MHz. The OPO delivers a signal output power of up to 280 mW at ∼35% extraction efficiency and can provide transform-limited signal pulses with durations of 0.4 ps over the spectral range of 1.00–1.14 μm. © 2000 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking

Terahertz demultiplexing by a single-shot time-to-space conversion using a film of squarylium dye J aggregates

Makoto Furuki, Minquan Tian, Yasuhiro Sato, Lyong Sun Pu, Satoshi Tatsuura, and Osamu Wada

Appl. Phys. Lett. 77, 472 (2000); http://dx.doi.org/10.1063/1.127014 (3 pages) | Cited 35 times

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We applied time-to-space conversion using femtosecond nonlinear-optical response of squarylium-dye (SQ) J-aggregates film. A pump pulse and a train of four probe pulses were illuminated on the same area (10 mm ϕ) of the film in direction of oblique and normal to the film plane, respectively. Due to the oblique illumination, the pump pulse met probe pulses (interval time: 1 ps) at separate places. The film picked out part of each probe pulse by its transmittance change, which was observed for a transmitted image of spatially separated four lines. Response time of the SQ J aggregates is enough for the single-shot 1 THz demultiplexing. © 2000 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Wc Optical coatings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.70.Mp Nonlinear optical crystals
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Current injection emission from a transparent p–n junction composed of p-SrCu2O2/n-ZnO

Hiromichi Ohta, Ken-ichi Kawamura, Masahiro Orita, Masahiro Hirano, Nobuhiko Sarukura, and Hideo Hosono

Appl. Phys. Lett. 77, 475 (2000); http://dx.doi.org/10.1063/1.127015 (3 pages) | Cited 268 times

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An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron–hole plasma of ZnO. © 2000 American Institute of Physics.
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73.61.Ga II-VI semiconductors
73.61.Le Other inorganic semiconductors
78.66.Hf II-VI semiconductors
85.60.Jb Light-emitting devices
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Fg Pulsed laser ablation deposition
85.40.Hp Lithography, masks and pattern transfer
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.05.Dz II-VI semiconductors

Visible emission from electroluminescent devices using an amorphous AlN:Er3+ thin-film phosphor

V. I. Dimitrova, P. G. Van Patten, H. H. Richardson, and M. E. Kordesch

Appl. Phys. Lett. 77, 478 (2000); http://dx.doi.org/10.1063/1.127016 (2 pages) | Cited 39 times

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Electroluminescence (EL) studies of AlN:Er alternating-current thin-film electroluminescent (ACTFEL) devices were performed at 300 K. Thin films of Er-doped AlN, ∼ 200 nm thick, were grown on indium–tin–oxide/aluminum–titanium–oxide/glass substrates using rf magnetron sputtering in a nitrogen atmosphere. The turn-on voltage was found to be around 70–80 and 100 V for ACTFEL devices without and with a top insulator layer. Sharp emission lines in the visible region were observed which correspond to known transitions of the Er3+ ion. Temperature-dependent cathodoluminescence studies corroborate the EL results, and show that optimum device performance is attained near 300 K. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices
78.60.Hk Cathodoluminescence, ionoluminescence
78.60.Fi Electroluminescence

Diffraction of guided optical waves by surface acoustic waves in GaN

R. Rimeika, D. Ciplys, R. Gaska, J. W. Yang, M. A. Khan, M. S. Shur, and E. Towe

Appl. Phys. Lett. 77, 480 (2000); http://dx.doi.org/10.1063/1.127017 (3 pages) | Cited 13 times

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We report on acousto-optical diffraction of the guided optical modes (λ = 633 nm) in GaN layers grown on (0001) sapphire substrates. The diffraction of both transverse electric (TE) and transverse magnetic (TM) modes has been observed. The dependence of the diffraction efficiency on the surface acoustic wave (SAW) power is in good agreement with Raman-Nath theory. The values of acousto-optic figure of merit, M2, and effective photoelastic constants p have been determined. For the SAW propagating in [1math00] direction, the extracted values are M2 = 1.54×10−15 s3/kg, p = 0.061 (TE modes) and M2 = 1.95×10−15 s3/kg, p = 0.066 (TM modes). These values of M2 correspond to 1 and 1.3 of the acousto-optic figure for fused quartz. The obtained results demonstrate the potential of GaN-based structures for the development of blue–ultraviolet acousto-optical devices. © 2000 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.79.Gn Optical waveguides and couplers

Upconversion luminescence of Er3+ in alkali bismuth gallate glasses

S. Q. Man, E. Y. B. Pun, and P. S. Chung

Appl. Phys. Lett. 77, 483 (2000); http://dx.doi.org/10.1063/1.127018 (3 pages) | Cited 66 times

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Frequency upconversion of Er3+ in alkali bismuth gallate glasses have been investigated. The upconversion mechanisms are discussed, and the dominant mechanisms are excited state absorption for the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions, and energy transfer upconversion for the 4F9/2→4I15/2 transition. Intense green (around 525–550 nm) and red (around 660 nm) emission bands were observed under 800 nm excitation. At a pump intensity of 15.6 W/cm2, frequency upconversion efficiencies of 2.1×10−2 and 4.8×10−3 were obtained for the green and red emissions, respectively. The results are the highest among doped oxide glasses, and are comparable to those reported for Er3+/Yb3+ codoped fluoride glasses. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials

Electro-optic field mapping system utilizing external gallium arsenide probes

K. Yang, L. P. B. Katehi, and J. F. Whitaker

Appl. Phys. Lett. 77, 486 (2000); http://dx.doi.org/10.1063/1.127019 (3 pages) | Cited 27 times

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External electro-optic probes fabricated from two different crystal orientations of GaAs have been implemented in an electro-optic sampling system that is capable of mapping three independent orthogonal components of free-space electric fields. The results obtained for the radiated field from a microstrip patch antenna by the GaAs probes are compared with results on the same antenna obtained using bismuth silicate and lithium tantalate probes. An 8 μm spatial resolution has also been demonstrated for the electro-optic field-mapping system, and the capability for the system to measure field patterns at frequencies up to 100 GHz has been shown. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
84.40.Ba Antennas: theory, components and accessories
61.50.-f Structure of bulk crystals
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Functional separation of biasing and sustaining voltages in two-frequency capacitively coupled plasma

T. Kitajima, Y. Takeo, Z. Lj. Petrović, and T. Makabe

Appl. Phys. Lett. 77, 489 (2000); http://dx.doi.org/10.1063/1.127020 (3 pages) | Cited 110 times

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Separation of the effects of rf sources used for biasing the wafer and for sustaining the plasma is studied by measuring the space profiles of net excitation rate of Ar(3p5) for a two-frequency capacitively coupled plasma as a representation of a typical oxide etcher. Measurements were performed in Ar and in CF4/Ar mixtures. For biasing supply operating at low frequency, 700 kHz, it was shown that the effect of the voltage becomes significantly smaller as the sustaining voltage is changed from high frequency, 13.56 MHz, to very high frequency (VHF), 100 MHz, and it even disappears for pulsed operation in mixtures. This is the result of the low dc self-bias at the VHF electrode that allows the high energy secondary electrons to leave the plasma without excessive contribution to ionization and dissociation. © 2000 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Antenna configuration for uniform large-area inductively coupled plasma production

S. S. Kim, H. Y. Chang, C. S. Chang, and N. S. Yoon

Appl. Phys. Lett. 77, 492 (2000); http://dx.doi.org/10.1063/1.127021 (3 pages) | Cited 23 times

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An antenna configuration for uniform plasma generation in a large-area inductively coupled plasma (ICP) source is presented and investigated using numerical analysis. The numerical results show that a properly tuned, segmented coil system with an external variable capacitor can allow antenna voltage, currents, and plasma uniformity to be controlled in the large-area ICP source. The key element of this concept is to induce LC-resonance in the coil system by the external capacitance variation. Through the LC-resonance, not only a small antenna voltage can be obtained, but also a selected coil current near a low plasma density regime can be significantly enhanced. Self-consistent fluid simulations for Ar and Cl2 plasmas indicate that the radial plasma spread can be optimized near the LC-resonance condition. © 2000 American Institute of Physics.
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52.50.-b Plasma production and heating
52.65.-y Plasma simulation
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides

Measurement of negative-ion density in high-density C4F8 plasma using a laser photodetachment technique combined with a millimeter-wave open resonator

A. Kono and K. Kato

Appl. Phys. Lett. 77, 495 (2000); http://dx.doi.org/10.1063/1.127022 (3 pages) | Cited 8 times

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A technique for measuring negative-ion density in high-density plasmas used for materials processing has been developed; negative ions were detected by measuring the electron-density perturbation caused by laser photodetachment using a millimeter-wave open resonator. The measured negative-ion density for an inductively-coupled C4F8(5%–20%)/Ar plasma with electron densities around 1011 cm−3 at a pressure of 25 mTorr was comparable to the electron density. The results suggest that species produced via dissociation of C4F8 attaches electrons as effectively as C4F8. © 2000 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties
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Influence of sample oxidation on the nature of optical luminescence from porous silicon

I. Coulthard, W. J. Antel, J. W. Freeland, T. K. Sham, S. J. Naftel, and P. Zhang

Appl. Phys. Lett. 77, 498 (2000); http://dx.doi.org/10.1063/1.127023 (3 pages) | Cited 12 times

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Site-selective luminescence experiments were performed upon porous-silicon samples exposed to varying degrees of oxidation. The source of different luminescence bands was determined to be due to either quantum confinement in nanocrystalline silicon or defective silicon oxide. Of particular interest is the defective silicon-oxide luminescence band found at 2.1 eV, which was found to frequently overlap with a luminescence band from nanocrystalline silicon. Some of the historical confusion and debate with regards to the source of luminescence from porous silicon can be attributed to this overlap. © 2000 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.55.Mb Porous materials
81.65.Mq Oxidation

Friction contrast in resonant cantilever vibration mode

A. Spychalski-Merle, K. Krischker, T. Göddenhenrich, and C. Heiden

Appl. Phys. Lett. 77, 501 (2000); http://dx.doi.org/10.1063/1.127024 (3 pages) | Cited 6 times

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The dynamic scanning friction microscopy technique is based on a well-known lateral sample modulation technique combined with a lock-in amplifier. In this paper, we describe a modified detection scheme in the resonant regime of a cantilever’s bending mode. This resonant mode leads to a couple of advantages in the imaging mode especially applicable under ultrahigh vacuum conditions, as well as an additional spectroscopy mode by measuring the resonance curve. An interpretation of the resonance curves and the images in terms of the friction losses is given, taking into account the cantilever vibration and the observed nonlinear characteristic of the stick–slip interaction. © 2000 American Institute of Physics.
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07.79.Sp Friction force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
62.20.Qp Friction, tribology, and hardness

Size-dependent picosecond energy relaxation in PbSe quantum dots

Tsuyoshi Okuno, Yasuaki Masumoto, Michio Ikezawa, Tomoyasu Ogawa, and Andrey A. Lipovskii

Appl. Phys. Lett. 77, 504 (2000); http://dx.doi.org/10.1063/1.127025 (3 pages) | Cited 17 times

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We measured the size dependence of the energy relaxation time of PbSe quantum dots at room temperature. The radius of the dots was evaluated by small-angle x-ray scattering. We found a monotonic decrease of the relaxation time from 25 to 1 ps with a decrease of the radius r from 2.9 to 1.4 nm. The 1/r3 dependence of the relaxation rate was indicated. © 2000 American Institute of Physics.
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78.66.Li Other semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.70.Ck X-ray scattering
78.47.-p Spectroscopy of solid state dynamics

Direct evidence of spontaneous quantum dot formation in a thick InGaN epilayer

L. Nistor, H. Bender, A. Vantomme, M. F. Wu, J. Van Landuyt, K. P. O’Donnell, R. Martin, K. Jacobs, and I. Moerman

Appl. Phys. Lett. 77, 507 (2000); http://dx.doi.org/10.1063/1.127026 (3 pages) | Cited 29 times

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We report a direct observation of quantum dots formed spontaneously in a thick InGaN epilayer by high resolution transmission electron microscopy. Investigation of a (280 nm thick) In0.22Ga0.78N single layer, emitting in the blue/green spectral region, reveals quantum dots with estimated sizes in the range of 1.5–3 nm. Such sizes are in very good agreement with calculations based on the luminescence spectra of this specimen. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Saturation of THz-frequency intraband absorption in InAs/GaAs quantum dot molecules

P. Boucaud, K. S. Gill, J. B. Williams, M. S. Sherwin, W. V. Schoenfeld, and P. M. Petroff

Appl. Phys. Lett. 77, 510 (2000); http://dx.doi.org/10.1063/1.127027 (3 pages) | Cited 15 times

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We have investigated the far-infrared absorption in InAs/GaAs quantum dot molecules. The quantum dot molecules consist of two vertically coupled InAs self-assembled quantum dots separated by a GaAs barrier. The electronic coupling between the dot states results in an intraband absorption at THz frequencies. We show that this absorption can be bleached under high excitation intensity delivered by a free-electron laser. The saturation intensity is found to be on the order of 1 W cm−2. The electron relaxation time T1 is estimated from the saturation intensity. A lower limit for T1 of the order of 30 ps is deduced. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.47.-p Spectroscopy of solid state dynamics
73.61.Ey III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Effect of multidirection rubbing on the alignment of nematic liquid crystal

Young Jin Kim, Zhizhong Zhuang, and Jay S. Patel

Appl. Phys. Lett. 77, 513 (2000); http://dx.doi.org/10.1063/1.127028 (3 pages) | Cited 9 times

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We have investigated the alignment properties of liquid crystals induced by multiple rubbing of the surfaces in different directions. Experiments were carried out using homeotropic and hybrid-aligned samples. It is experimentally found that the alignment of the liquid crystals is along neither of the rubbing directions, but instead lies along an axis intermediate between these two directions, and that the direction depended on the relative strength of rubbing along the two axes. A model that assumed the grooves along two rubbing directions is proposed, and the relation between the orientation of the liquid crystal and the relative rubbing strength is analyzed. We found that this model can explain the observed experimental results. © 2000 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures

Morphological instability of growth fronts due to stress-induced mobility variations

Jennifer F. Sage, William Barvosa-Carter, and Michael J. Aziz

Appl. Phys. Lett. 77, 516 (2000); http://dx.doi.org/10.1063/1.127029 (3 pages) | Cited 17 times

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We report a comparison between theory and experiment for a general stress-induced morphological growth instability that is kinetically rather than energetically driven. Stress variations along a perturbed planar growth front result in variations in interfacial mobility in a manner that is destabilizing under one sign of the stress state and stabilizing under the opposite sign, even for a pure material. Investigation of solid-phase epitaxial growth at a corrugated Si(001) interface under both compression and tension results in good agreement between experiment and theory with no adjustable parameters, demonstrating that this mobility-based mechanism is dominant in determining morphological evolution in this system. © 2000 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.35.Gy Mechanical properties; surface strains
68.55.-a Thin film structure and morphology
81.15.Np Solid phase epitaxy; growth from solid phases
68.35.Ct Interface structure and roughness

Raman study of ZnxBe1−xSe alloy (100) epitaxial layers

O. Pagès, M. Ajjoun, J. P. Laurenti, D. Bormann, C. Chauvet, E. Tournié, and J. P. Faurie

Appl. Phys. Lett. 77, 519 (2000); http://dx.doi.org/10.1063/1.127030 (3 pages) | Cited 16 times

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Long wavelength longitudinal optical (LO) and transverse optical (TO) phonons of BeSe and ZnxBe1−xSe layers are identified in a wide composition range by using Raman spectroscopy. A two-mode behavior is clearly evidenced. As predicted by the dielectric model of Hon and Faust, the eigenfrequencies of the BeSe- and ZnSe-like LO modes correspond to the maxima of Im〈−ε(ω, x)−1〉. Excellent agreement is obtained with a model where the calculations are performed by using the equations of motion and polarization derived from the modified random element isodisplacement model. Besides, the TO and LO frequencies for BeSe are determined to be 501 and 579 cm−1, respectively. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Optical microcavities based on amorphous silicon–nitride Fabry–Pérot structures

Fabrizio Giorgis

Appl. Phys. Lett. 77, 522 (2000); http://dx.doi.org/10.1063/1.127031 (3 pages) | Cited 26 times

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All amorphous silicon–nitride (a-Si1−xNx:H) optical microcavities have been grown by plasma-enhanced chemical vapor deposition. The basic structure is a Fabry–Pérot resonator with a N-rich a-Si1−xNx:H layer as optical active medium. By controlling layer thickness and composition, homogeneous structures have been obtained on a large area. Tunable narrow emission bands (few nm) and a strong resonant enhancement of the luminescence yield (more than 1 order of magnitude) have been demonstrated. These results, which can be accounted for by a light intensity spatial redistribution owing to the anisotropic phonon density of states in the cavities, open up new possibilities for applications in thin film flat panel displays. © 2000 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Hx Other solid inorganic materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
81.05.Gc Amorphous semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Crystallization of bulk amorphous Zr–Ti(Nb)–Cu–Ni–Al

Jörg F. Löffler, Sven Bossuyt, Stephen C. Glade, William L. Johnson, Werner Wagner, and P. Thiyagarajan

Appl. Phys. Lett. 77, 525 (2000); http://dx.doi.org/10.1063/1.127032 (3 pages) | Cited 38 times

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Small-angle neutron scattering (SANS) and transmission electron microscopy were used to resolve the crystallization of the bulk amorphous alloys Zr52.5Ti5Cu17.9Ni14.6Al10 (Vit105) and Zr57Nb5Cu15.4Ni12.6Al10 (Vit106). Decomposition and nanocrystallization were observed in both alloy compositions in the temperature regime from the glass transition, Tg, up to at least 90 K above Tg. From in situ SANS measurements on Vit105, chemical diffusion data were obtained whose temperature dependence follows an Arrhenius law. Normalizing the temperature to Tg, the diffusion data of Vit105 are very similar to those of the well-investigated bulk amorphous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5. © 2000 American Institute of Physics.
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81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Precipitation of icosahedral quasicrystalline phase in Hf65Al7.5Ni10Cu12.5Pd5 metallic glass

Chunfei Li, Junji Saida, Mitsuhide Matsushita, and Akihisa Inoue

Appl. Phys. Lett. 77, 528 (2000); http://dx.doi.org/10.1063/1.127033 (3 pages) | Cited 26 times

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An icosahedral quasicrystalline phase was found in a Hf65Al7.5Ni10Cu12.5Pd5 metallic glass annealed in the supercooled liquid region. Upon annealing at high temperature, the quasicrystalline phase was found to decompose to regular crystalline phases, indicating that it is a metastable phase. The present alloy was compared with the previously reported Zr- and Ti-based alloys with the formation of icosahedral quasicrystalline phases. Hf, Zr, and Ti belong to the same 4A column in the element periodical table. Based on the above comparison, conditions in terms of atomic radius and alloy composition which favor the formation of icosahedral quasicrystalline phase in 4A element based alloys, were suggested. © 2000 American Institute of Physics.
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81.30.Mh Solid-phase precipitation
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
64.75.-g Phase equilibria
61.44.Br Quasicrystals
81.40.Gh Other heat and thermomechanical treatments

A formation mechanism of carbon nanotube films on SiC(0001)

M. Kusunoki, T. Suzuki, T. Hirayama, N. Shibata, and K. Kaneko

Appl. Phys. Lett. 77, 531 (2000); http://dx.doi.org/10.1063/1.127034 (3 pages) | Cited 69 times

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We report a remarkable difference of decomposed structures on the Si(0001) and C(0001) faces of a SiC single crystal observed by using a cross-sectional high-resolution electron microscopy. An aligned carbon nanotube (CNT) film was fabricated on the C face perpendicular to the surface after heating at 1700 °C for half an hour in a vacuum. On the contrary, a very thin layer of graphite sheets parallel to the surface was formed on the Si face under the same condition. It is proposed that the growth of CNTs is determined by the generation of nanocaps at the initial stage, by comparing the difference of the decomposition mechanisms on the both faces. © 2000 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Stacking fault energies in Si doped GaN: A first principles study

J. A. Chisholm and P. D. Bristowe

Appl. Phys. Lett. 77, 534 (2000); http://dx.doi.org/10.1063/1.127035 (3 pages) | Cited 4 times

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The variation of stacking fault energy in GaN as a function of silicon doping is calculated using density functional theory. It is found that the stacking fault energy reduces with increasing silicon concentration in agreement with experimental observations of higher stacking fault densities in Si doped GaN compared to undoped GaN. The result is explained in terms of a decrease in the magnitude of the Mulliken charges on the atoms as silicon is incorporated into the lattice and an increase in the overlap populations. We propose that Mulliken charges can be used to predict how any substitutional impurity will influence the stacking fault formation energy. © 2000 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
61.72.Bb Theories and models of crystal defects
81.05.Ea III-V semiconductors
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