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21 Jul 2003

Volume 83, Issue 3, pp. 407-587

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 575 (2003); http://dx.doi.org/10.1063/1.1594830 (3 pages)

P. Yu, M. Mustata, J. J. Turek, P. M. W. French, M. R. Melloch, and D. D. Nolte
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Location control of crystal grains in excimer laser crystallization of silicon thin films

Hideya Kumomi

Appl. Phys. Lett. 83, 434 (2003); http://dx.doi.org/10.1063/1.1591998 (3 pages) | Cited 11 times

Online Publication Date: 16 July 2003

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Location of crystal grains in polycrystalline Si thin films formed by excimer-laser crystallization is controlled by manipulating the superlateral-growth phenomenon. The superlateral growth of a single grain occurs preferentially at an artificial site where nanometer-sized crystallites are embedded in the precursory amorphous thin films. Only a part of the crystallites embedded in the site could survive the melting and grow to serve as the seed crystal in the subsequent recrystallization. Such grain-location control provides a basis for two-dimensional control of the grain-boundary location in low-temperature polycrystalline Si thin films, which is essential to the device-to-device uniformity of high-performance thin-film transistors. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
64.70.K- Solid-solid transitions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.46.-w Structure of nanoscale materials
61.82.Fk Semiconductors
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)

Negative-U property of the oxygen vacancy defect in SiO2 and its implication for the E1′ center in α-quartz

D. J. Chadi

Appl. Phys. Lett. 83, 437 (2003); http://dx.doi.org/10.1063/1.1592003 (3 pages) | Cited 6 times

Online Publication Date: 16 July 2003

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The +1 charged state of an oxygen vacancy V(O)+ in α-quartz is found to be unstable with respect to the reaction 2V(O)+→V(O)0+V(O)2+, which lowers the total energy by 2.9 eV, making it highly unlikely that V(O)+ is the source of the electron-paramagnetic-resonance (EPR) active E1′ center in α-quartz. Results from ab initio total energy calculations indicate that V(SiO3)+ and V(SiO4)+ are the smallest EPR active vacancy complexes. The atomic and electronic structures of these two multivacancy clusters are surprisingly similar to those of V(O)+. © 2003 American Institute of Physics.
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76.30.Mi Color centers and other defects
61.72.J- Point defects and defect clusters
71.55.Ht Other nonmetals
71.15.-m Methods of electronic structure calculations

Nanoshell tubes of ferroelectric lead zirconate titanate and barium titanate

Yun Luo, Izabela Szafraniak, Nikolai D. Zakharov, Valanoor Nagarajan, Martin Steinhart, Ralf B. Wehrspohn, Joachim H. Wendorff, Ramamoorthy Ramesh, and Marin Alexe

Appl. Phys. Lett. 83, 440 (2003); http://dx.doi.org/10.1063/1.1592013 (3 pages) | Cited 77 times

Online Publication Date: 16 July 2003

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Wafer-scale fabrication of ferroelectric oxide nanoshell tubes as well as ordered nanotube arrays have been accomplished using a simple and convenient fabrication method that allows full tailoring of tube dimensions as well as array pattern and size. Using different silicon and alumina templates, barium titanate and lead zirconate titanate tubes with diameters ranging from 50 nm up to several micrometers meter and lengths of more 100 μm have been fabricated. Ferroelectric switching of submicrometer tubes has been shown using piezoresponse scanning probe microscopy. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.07.De Nanotubes
61.46.-w Structure of nanoscale materials
77.80.Fm Switching phenomena
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
77.65.Bn Piezoelectric and electrostrictive constants

Wavelength selective charge storage in self-assembled InGaAs/GaAs quantum dots

M. Kroutvar, Y. Ducommun, J. J. Finley, M. Bichler, G. Abstreiter, and A. Zrenner

Appl. Phys. Lett. 83, 443 (2003); http://dx.doi.org/10.1063/1.1588368 (3 pages) | Cited 26 times

Online Publication Date: 16 July 2003

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We present a wavelength selective optical memory device based on optically-induced charge storage in an inhomogeneously broadened ensemble of InGaAs quantum dots. We show that electrons and holes can be efficiently and resonantly stored without thermal redistribution of charge between dots over timescales much longer than 25 μs at 10 K. Direct information on the absorption mechanisms are obtained for self-assembled dots. The maximum efficiency of the charge storage process is estimated to be close to unity. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

In situ lateral growth control of optically efficient quantum structures

T. Schallenberg, W. Faschinger, G. Karczewski, L. W. Molenkamp, V. Türck, S. Rodt, R. Heitz, D. Bimberg, M. Obert, G. Bacher, and A. Forchel

Appl. Phys. Lett. 83, 446 (2003); http://dx.doi.org/10.1063/1.1592894 (3 pages) | Cited 7 times

Online Publication Date: 16 July 2003

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We present a versatile method for in situ lateral growth control of optically efficient quantum structures. The method is based on molecular-beam epitaxy through an epitaxial shadow mask. Lateral control is achieved by selective area growth of short period superlattices. We demonstrate how the method can be applied to both lattice-matched and unmatched material systems. In the former, selective growth is employed in the formation of quantum wires. In the latter, this growth concept was also successfully applied to control the self-assembly of quantum dots within selected areas. The excellent quality of the quantum structures is demonstrated by their bright cathodoluminescence at room temperature. © 2003 American Institute of Physics.
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81.07.Ta Quantum dots
78.67.Hc Quantum dots
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Photostimulated luminescence in Eu-doped fluorochlorozirconate glass ceramics

Stefan Schweizer, Linn W. Hobbs, Mihail Secu, Johann-Martin Spaeth, Andrew Edgar, and Grant V. M. Williams

Appl. Phys. Lett. 83, 449 (2003); http://dx.doi.org/10.1063/1.1593228 (3 pages) | Cited 41 times

Online Publication Date: 16 July 2003

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We report the synthesis of Eu2+- and chlorine-doped fluorozirconate glass-ceramics that show an intense photostimulated luminescence (PSL) after x-ray irradiation at room temperature. The PSL efficiency is up to 80% of that found in the well-known crystalline x-ray storage phosphor BaFBr:Eu2+, and it is the largest thus far reported for a glass-ceramic. We attribute the PSL to crystallites of orthorhombic BaCl2 that are formed after annealing above the glass temperature. Hexagonal BaCl2 crystallites are also observed after short annealing times, but they do not provide a measurable PSL signal. The photoluminescence peak from glass-ceramics containing orthorhombic BaCl2 crystallites occurs at 402 nm, and the stimulation band is centered at about 560 nm. © 2003 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing

Near-surface characterization of amorphous carbon films by neutron reflectivity

J. A. Johnson, J. B. Woodford, A. Erdemir, and G. R. Fenske

Appl. Phys. Lett. 83, 452 (2003); http://dx.doi.org/10.1063/1.1590731 (3 pages) | Cited 17 times

Online Publication Date: 16 July 2003

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A high-density top-surface layer of approximately 30 Å was found in a form of diamondlike carbon, “near-frictionless carbon,” developed at Argonne National Laboratory. Three diamondlike-carbon films were prepared by plasma-enhanced chemical vapor deposition with different hydrogen-to-methane ratios in the plasma. Complementary films were prepared with deuterated methane and deuterium, in the same ratios. Results from neutron relectivity experiments are presented, along with model comparisons, and a hypothesis is postulated. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Abnormal electrical resistivity in γ-TiAl thin films deposited by magnetron sputtering

T. L. Alford, K. S. Gadre, H. C. Kim, and S. C. Deevi

Appl. Phys. Lett. 83, 455 (2003); http://dx.doi.org/10.1063/1.1593826 (3 pages) | Cited 3 times

Online Publication Date: 16 July 2003

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Thin films of γ-TiAl are being considered as a potential conductor and/or diffusion barrier for high temperature electronics because of their high melting points and high oxidation resistance. However, it is not possible to form pure γ-TiAl thin films by thermal annealing of Al/Ti bilayers. This study, however, demonstrates the formation of γ-TiAl thin films by dc magnetron sputtering of a compound target. X-ray diffractometry and Rutherford backscattering spectrometry analyses confirm the γ-TiAl phase formation, composition, and thermal stability in vacuum (up to 700 °C, 1 h) on SiO2. Four-point probe resistivity measurements in vacuum show an initial increase in the resistivity with temperature up to transition temperature for the γ-TiAl thin films. At higher temperatures a decrease in resistivity with additional heating (i.e., negative temperature coefficient of resistivity, TCR) is seen. The values of dρ/dT are typically on the order of −0.32 μΩ cm/°C between 200 and 550 °C. At the highest temperature, a minimum value of resistivity of ∼ 13 μΩ cm is obtained; this value is about one half the value of bulk TiAl at room temperatures. The negative TCR, low resistivity values at high temperatures, and temperature stability are not typically seen in bulk TiAl. This abnormal electrical property is explained using a modified model for a thermally activated polaron-hopping mechanism. © 2003 American Institute of Physics.
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73.61.At Metal and metallic alloys
81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
68.55.Nq Composition and phase identification
68.60.Dv Thermal stability; thermal effects
72.60.+g Mixed conductivity and conductivity transitions

Irradiation-induced recovery of disorder in gallium nitride

W. Jiang and W. J. Weber

Appl. Phys. Lett. 83, 458 (2003); http://dx.doi.org/10.1063/1.1594282 (3 pages) | Cited 8 times

Online Publication Date: 16 July 2003

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Gallium nitride has been irradiated to two fluences with energetic Au2+ ions at 300 K. Two different damage levels and depth profiles were produced that are characterized by near-surface damage accumulation and deeper-regime damage saturation. Thermal annealing at 873 K resulted in disorder recovery only in the near-surface region at low fluence. However, simultaneous irradiation with 5.4 MeV Si2+ ions during annealing at 873 K induced significant recovery over the entire damage profile at both low and high fluences. The irradiation-enhanced recovery is primarily attributed to defect-stimulated recovery and epitaxial recrystallization processes due to the creation of mobile Frenkel pairs. © 2003 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing

Short-period SinGem strained-layer superlattices grown from gas sources by synchrotron-radiation-excited chemical-beam epitaxy

Housei Akazawa

Appl. Phys. Lett. 83, 461 (2003); http://dx.doi.org/10.1063/1.1593795 (3 pages)

Online Publication Date: 16 July 2003

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Short-period SinGem strained-layer superlattices were successfully grown on Si (100) substrate from gas sources by synchrotron-radiation-excited chemical-beam epitaxy at 250 °C. Atomically sharp interfaces between the Si and Ge layers and two-dimensional morphology were obtained. With thinner Ge layers, the misfit strain is relieved by atomic-scale roughness at the interfaces; as the Ge layers become thicker, misfit dislocations become the main relief mechanism. The thickness of Si and Ge layers as derived from spectroscopic ellipsometry agreed nicely with images of the lattices. The dielectric constants of the growing Si and Ge top layers were much lower than those of Si and Ge bulk crystals, which is consistent with the mechanism of photoepitaxy, that is, the formation of a hydrogenated network as the precursor state followed by photolytic crystallization. © 2003 American Institute of Physics.
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68.65.Cd Superlattices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.82.Fk Semiconductors
61.80.Cb X-ray effects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Elastic–stiffness mapping by resonance-ultrasound microscopy with isolated piezoelectric oscillator

Hirotsugu Ogi, Jiayong Tian, Toyokazu Tada, and Masahiko Hirao

Appl. Phys. Lett. 83, 464 (2003); http://dx.doi.org/10.1063/1.1593819 (3 pages) | Cited 10 times

Online Publication Date: 16 July 2003

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A resonance-ultrasound microscopy has been developed for mapping a material’s elastic constant in a localized surface region. It detects the effective elastic modulus through a resonance frequency of free vibrations of a solid probe touching the specimen via a small tungsten-carbide bearing. Langasite (La3Ga5SiO14) crystal is used as a probe because of the low sensitivity of its elastic constants to temperature and its high piezoelectric coefficients. The vibration of the probe is excited and detected with a surrounding solenoid coil. This noncontacting acoustic coupling isolates the probe vibration and measures the resonance frequency with an accuracy better than one part in 105. This microscopic method is applied to a composite material consisting of silicon-carbide (SiC) fibers in titanium-alloy matrix. The stiffness distribution inside a single fiber was determined. © 2003 American Institute of Physics.
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81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.40.Jj Elasticity and anelasticity, stress-strain relations
43.35.Yb Ultrasonic instrumentation and measurement techniques
62.20.D- Elasticity
46.80.+j Measurement methods and techniques in continuum mechanics of solids
43.58.Ls Acoustical lenses and microscopes
07.10.Fq Vibration isolation

Structure of the nanocrystals in oxyfluoride glass ceramics

M. Beggiora, I. M. Reaney, and M. S. Islam

Appl. Phys. Lett. 83, 467 (2003); http://dx.doi.org/10.1063/1.1594842 (3 pages) | Cited 9 times

Online Publication Date: 16 July 2003

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The crystallization of fluoro-silicate glasses obtained using high-purity SiO2, AlO1.5, CdF2, PbF2, ZnF2, and ErF3 has been investigated. Upon heat treatment, PbF2 nanocrystals form which host most of the Er3+ ions. The major peaks obtained by x-ray diffraction suggest that the nanocrystals are fluorite structured, but the low volume fraction of nanocrystals and line broadening due to their small size mean that unambiguous identification of the crystal structure is impossible. Therefore, atomistic simulation techniques have been performed to investigate the mechanism of incorporation of Er3+ in the PbF2 nanocrystals and polycrystalline (1−x)PbF2–xErF3 ceramics have been fabricated to study the expected phase assemblage. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.05.Pj Glass-based composites, vitroceramics
81.07.Bc Nanocrystalline materials
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
81.40.Gh Other heat and thermomechanical treatments
61.66.Fn Inorganic compounds

Photoreflectance evidence of the N-induced increase of the exciton binding energy in an InxGa1−xAs1−yNy alloy

M. Geddo, G. Guizzetti, M. Capizzi, A. Polimeni, D. Gollub, and A. Forchel

Appl. Phys. Lett. 83, 470 (2003); http://dx.doi.org/10.1063/1.1594279 (3 pages) | Cited 10 times

Online Publication Date: 16 July 2003

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The binding energy of the heavy-hole ground-state exciton in In0.25Ga0.75As1−yNy/GaAs single quantum wells (y = 0, 0.011) was experimentally derived by photoreflectance measurements. We measured a binding energy of 6.6 and 8.5 meV for the N-free and the N-containing sample, respectively. The observed increase of the exciton binding energy can be accounted for by an increase of the exciton reduced mass of about 30% upon N introduction into the InxGa1−xAs lattice, consistently with recent experimental results and in agreement with earlier theoretical predictions. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.67.De Quantum wells
71.15.Nc Total energy and cohesive energy calculations

Measurement of the elastic constants of textured anisotropic thin films from x-ray diffraction data

P.-O. Renault, E. Le Bourhis, P. Villain, Ph. Goudeau, K. F. Badawi, and D. Faurie

Appl. Phys. Lett. 83, 473 (2003); http://dx.doi.org/10.1063/1.1594280 (3 pages) | Cited 24 times

Online Publication Date: 16 July 2003

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The elastic constants (compliances sij) of a textured anisotropic thin film deposited on a substrate have been determined. Using x-ray diffraction to measure the intragranular strain and a tensile machine to deform in situ the samples, an analytical method is described and has been developed for fiber textured thin films. The determination of thin film compliances only requires the knowledge of the substrate elastic constants. In the case of a 260-nm-thin gold film, the compliances were found to be slightly different from the corresponding bulk material ones. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity

Growth of InP quantum dots on vicinal GaAs (100) substrates by metalorganic chemical vapor deposition

X. B. Zhang, R. D. Heller, M. S. Noh, R. D. Dupuis, G. Walter, and N. Holonyak

Appl. Phys. Lett. 83, 476 (2003); http://dx.doi.org/10.1063/1.1595152 (3 pages) | Cited 5 times

Online Publication Date: 16 July 2003

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We report the growth of InP self-assembled quantum dots (QDs) on In0.5Al0.5P and In0.5(Al0.6Ga0.4)0.5P matrices, lattice matched on 0°, 2°, 6°, and 25° off-axis (100) GaAs substrates by metalorganic chemical vapor deposition. The influence of the substrate misorientation on the morphology and cathodoluminescence (CL) properties of the InP QDs was investigated. We find that the density of QDs grown on both In0.5Al0.5P and In0.5(Al0.6Ga0.4)0.5P matrices increases with the misorientation angle up to 6° off (100). At the same time, the dispersion of the QD size is getting larger for the growth on an In0.5Al0.5P matrix, but not for the growth on an In0.5(Al0.6Ga0.4)0.5P matrix. The InP QDs grown on In0.5(Al0.6Ga0.4)0.5P on 25° off-axis substrates are two-dimensionally well ordered. Moreover, the ordering improves and the density of QDs increases with an increase in the deposition of InP. The room-temperature CL intensity of InP QDs grown on a 25° off In0.5(Al0.6Ga0.4)0.5P is much stronger than that for InP QDs grown on a 25°-off In0.5Al0.5P matrix. © 2003 American Institute of Physics.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
78.60.Hk Cathodoluminescence, ionoluminescence
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