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14 May 2001

Volume 78, Issue 20, pp. 3003-3148

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High-quality porous-silicon buried waveguides

Andrea M. Rossi, Giampiero Amato, Vittorio Camarchia, Luca Boarino, and Stefano Borini

Appl. Phys. Lett. 78, 3003 (2001); http://dx.doi.org/10.1063/1.1370536 (3 pages) | Cited 20 times

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This letter reports a method to produce porous-silicon waveguides by means of a laser local oxidation process. The estimated losses of the waveguides are below 1 dB/cm. This demonstrates the applicability of this material in integrated optics and telecommunications. Moreover, our results disclose the opportunity to integrate optoelectronic devices onto Si substrates. The laser writing method is achievable at low laser power, thus it is highly efficient and achievable with the standard equipment present in most laboratories. Another advantage is that oxidation is achieved without heating the complete chip, thus simplifying the integration process, i.e., the oxidation is inherently local through the direct-write process. This method opens the opportunity to build microstructures, like channel and membrane filters, in a flexible manner by R&D laboratories. © 2001 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
81.65.Mq Oxidation
42.79.Ci Filters, zone plates, and polarizers
81.65.Cf Surface cleaning, etching, patterning

Simultaneously efficient blue and red light generations in a periodically poled LiTaO3

G. Z. Luo, S. N. Zhu, J. L. He, Y. Y. Zhu, H. T. Wang, Z. W. Liu, C. Zhang, and N. B. Ming

Appl. Phys. Lett. 78, 3006 (2001); http://dx.doi.org/10.1063/1.1371245 (3 pages) | Cited 23 times

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Generations of efficient blue light at 447 nm and red light at 671 nm were achieved by frequency doubling and tripling of a diode-pumped, Q-switched 1342 nm Nd:YVO4 laser with a periodically poled LiTaO3 (PPLT). The blue light at 447 nm was generated by sum-frequency mixing of the fundamental at 1342 nm with the generated second harmonic at 671 nm. The first-order and third-order reciprocals of the PPLT compensated the phase mismatches of second-harmonic and sum-frequency processes, respectively, making them quasiphase matched. The resulting averaged blue light power of 51 mW and red light power of 207 mW under the averaged fundamental power of 500 mW indicate that the PPLT may be used to construct an all-solid-state blue and red dual wavelength laser. © 2001 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.70.Hj Laser materials

Gain spectra of (GaIn)(NAs) laser diodes for the 1.3-μm-wavelength regime

M. Hofmann, A. Wagner, C. Ellmers, C. Schlichenmeier, S. Schäfer, F. Höhnsdorf, J. Koch, W. Stolz, S. W. Koch, W. W. Rühle, J. Hader, J. V. Moloney, E. P. O’Reilly, B. Borchert, A. Yu. Egorov, et al.

Appl. Phys. Lett. 78, 3009 (2001); http://dx.doi.org/10.1063/1.1371963 (3 pages) | Cited 44 times

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Optical gain spectra of (GaIn)(NAs)/GaAs quantum-well lasers operating in the 1.3-μm-emission-wavelength regime are measured and compared to those of a commercial (GaIn)(AsP)/InP structure. Good agreement of the experimental results with computed spectra of a microscopic many-body theory is obtained. Due to the contributions of a second confined subband, a spectrally broad gain region is expected for (GaIn)(NAs)/GaAs at elevated carrier densities. © 2001 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
73.21.Fg Quantum wells
78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Angle-dependent photocurrent spectroscopy of oxide-apertured vertical-cavity surface-emitting lasers during aging

A. Jaeger, P. M. Petroff, and T. D. Lowes

Appl. Phys. Lett. 78, 3012 (2001); http://dx.doi.org/10.1063/1.1371792 (3 pages) | Cited 10 times

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Aging properties of oxide-apertured vertical-cavity surface-emitting lasers have been analyzed by photocurrent (PC) measurements at room temperature. We demonstrate that this method allows an analysis of the aging process and provides insight into degradation mechanisms occurring during operation of these devices. By changing the angle of incidence in the PC experiment the energy positions of the top mirror features shift to higher energy while the excitonic transitions do not change. Thus, angle dependent PC spectra reveal both the appearance of defect bands located in the intrinsic region of the device as well as modifications of the top mirror transmission upon aging. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
73.50.Pz Photoconduction and photovoltaic effects

Strain-tunable photonic band gap crystals

Sungwon Kim and Venkatraman Gopalan

Appl. Phys. Lett. 78, 3015 (2001); http://dx.doi.org/10.1063/1.1371786 (3 pages) | Cited 58 times

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We have designed a two-dimensional strain-tunable photonic band gap crystal by distorting the symmetry of the crystal from a regular hexagonal to a quasihexagonal lattice by means of field driven strain using a piezoelectric material. Calculations predict that the original high symmetry energy bands split up into several strained energy bands depending on the magnitude and direction of the strain. In the proposed structures, we show that 2% (3%) shear strain can be used to tune ∼ 52% (73%) of the original undistorted absolute band gap of a two-dimensional photonic band gap crystal. These device structures can be used for optical switching and modulation. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
77.22.Ch Permittivity (dielectric function)
42.79.Hp Optical processors, correlators, and modulators
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Spatial control of second-order optical susceptibility induced in thermally poled glasses

H. Guillet de Chatellus, S. Montant, and E. Freysz

Appl. Phys. Lett. 78, 3018 (2001); http://dx.doi.org/10.1063/1.1371247 (3 pages)

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Second-order susceptibility thermally induced in poled glass samples was erased in doped borophosphate, lead silica, and fused silica glasses using an optical method. A simple law describes the temporal evolution and the spatial profile of the erased nonlinear region versus the intensity and profile of the erasure laser beam. A comparison is made between one and two photon absorption induced spatial profiles. © 2001 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
77.22.Ej Polarization and depolarization
42.70.Ce Glasses, quartz

Enhancement of second-harmonic generation in a one-dimensional semiconductor photonic band gap

Y. Dumeige, P. Vidakovic, S. Sauvage, I. Sagnes, J. A. Levenson, C. Sibilia, M. Centini, G. D’Aguanno, and M. Scalora

Appl. Phys. Lett. 78, 3021 (2001); http://dx.doi.org/10.1063/1.1372356 (3 pages) | Cited 96 times

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We demonstrate significant enhancement of second-order nonlinear interactions in a one-dimensional semiconductor Bragg mirror operating as a photonic band gap structure. The enhancement comes from a simultaneous availability of a high density of states, thanks to high field localization, and the improvement of effective coherent length near the photonic band edge. © 2001 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Qs Photonic bandgap materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
73.21.Ac Multilayers
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Submicron three-dimensional infrared GaAs/AlxOy-based photonic crystal using single-step epitaxial growth

Jayshri Sabarinathan, Pallab Bhattacharya, Donghai Zhu, Boaz Kochman, Weidong Zhou, and Pei-Chen Yu

Appl. Phys. Lett. 78, 3024 (2001); http://dx.doi.org/10.1063/1.1372198 (3 pages) | Cited 2 times

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A relatively simple technique is demonstrated to fabricate three-dimensional face-centered-cubic infrared photonic crystals with submicron feature sizes using GaAs-based technology, single-step epitaxial growth, and lateral wet oxidation. The photonic crystals were fabricated with feature sizes (a) of 1.5 and 0.5 μm. Transmission measurements reveal a stopband centered at 1.0 μm with a maximum attenuation of 10 dB for the submicron (a = 0.5 μm) photonic crystal. This technique is scalable to small photonic crystal periodicity and hence to shorter wavelengths. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
81.05.Ea III-V semiconductors
81.65.Mq Oxidation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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Electrode sheath voltage in pulsed high-pressure mercury arcs

A. Kloss, H. Schneidenbach, and H. Hess

Appl. Phys. Lett. 78, 3027 (2001); http://dx.doi.org/10.1063/1.1371793 (2 pages) | Cited 4 times

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The electric field strength and the electrode sheath voltage in high-pressure mercury arcs were experimentally determined for operation in a current-pulse mode. The current was sinusoidally alternating with a basic frequency of 50 Hz. Each fifth half cycle was pulsed with different ratios of the maximum current in the pulse to those in the other four half cycles. The experimental results quite well agree with model calculations considering radiation transport. The most impressive feature of the electrode sheath voltage is a very pronounced minimum immediately after the reignition peak which can reach high negative values. © 2001 American Institute of Physics.
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52.50.Nr Plasma heating by DC fields; ohmic heating, arcs
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.40.Kh Plasma sheaths
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Electric field modulation spectroscopy by scanning tunneling microscopy with a nanometer-scale resolution

Akira Hida, Yutaka Mera, and Koji Maeda

Appl. Phys. Lett. 78, 3029 (2001); http://dx.doi.org/10.1063/1.1369385 (3 pages) | Cited 10 times

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Instrumentation has been devised by coupling electric field modulation spectroscopy (EFMS) with scanning tunneling microscopy (STM) that enables the investigation of electronic band structures in semiconductors with a nanometer-scale spatial resolution. Model experiments using low-temperature-grown GaAs (LT–GaAs) epifilms show that a difference as small as 0.01 eV in electronic energy gaps between the GaAs substrate and the LT–GaAs epilayers can be distinguished in the EFMS spectra, demonstrating the high energy, as well as spatial, resolution of the STM–EFMS. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
07.60.Rd Visible and ultraviolet spectrometers
78.20.Jq Electro-optical effects
71.20.Nr Semiconductor compounds

Electronic properties of α-Sn(100)2×1: Evidence for asymmetric dimer reconstruction

A. Cricenti, P. Perfetti, N. Barret, C. Guillot, V. Yu. Aristov, and G. Le Lay

Appl. Phys. Lett. 78, 3032 (2001); http://dx.doi.org/10.1063/1.1369416 (3 pages) | Cited 2 times

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A well-ordered thick layer of α-Sn(100) has been grown on InSb(100). The low energy electron diffraction pattern showed a sharp 2×1 double domain reconstruction with very low background at room temperature. The electronic properties have been studied by core-level- and angle-resolved photoemission spectroscopy (ARPES). ARPES spectra showed the presence of a surface state at normal emission, 1.15 eV below the Fermi level. This state disperses downward 1.3 eV along the [010] direction. Core-level spectra are well fitted with three surface-shifted components at binding energies +0.22, −0.23, and −0.49 eV with respect to the bulk component. Such results are in agreement with theoretical calculations based on asymmetric dimers by [Z.-Y. Lu, G. Chiarotti, S. Scandolo, and E. Tosatti, Phys. Rev. B 58, 13698 (1998)], taking into account final state effects, and exclude the existence of symmetric dimers. © 2001 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Zone-folding effect on optical phonon in GaN/Al0.2Ga0.8N superlattices

C. H. Chen, Y. F. Chen, An Shih, S. C. Lee, and H. X. Jiang

Appl. Phys. Lett. 78, 3035 (2001); http://dx.doi.org/10.1063/1.1369389 (3 pages) | Cited 14 times

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Optical properties of GaN/Al0.2Ga0.8N superlattices have been investigated by Raman scattering and photoluminescence measurements. It is found that the A1(LO) phonon decreases in frequency with decreasing quantum-well width. The frequency shift is attributed to the effect of phonon zone folding. Through the study of photoluminescence, we show that our observation of the zone-folding effect on optical phonon in GaN/Al0.2Ga0.8N superlattices is due to the sharpness of the interfaces between barrier and well layers. The sharp interfaces prevent the appearance of mixed interface modes which mask the phonon effect of zone folding in previous reports. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
73.21.Cd Superlattices
68.35.Ct Interface structure and roughness

Surfactant effects on doping of GaAs grown by organometallic vapor phase epitaxy

J. K. Shurtleff, S. W. Jun, and G. B. Stringfellow

Appl. Phys. Lett. 78, 3038 (2001); http://dx.doi.org/10.1063/1.1371790 (3 pages) | Cited 10 times

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Recently, the addition of the isoelectronic surfactant Sb during organometallic vapor phase epitaxy (OMVPE) of GaInP was shown to eliminate ordering, resulting in a significant change in the band gap energy. These results suggest that surfactants added during growth could have profound affects on other important properties of semiconductors, such as doping. This letter presents the results of a recent study on the effects of the isoelectronic surfactant Sb on doping in GaAs. The addition of a small amount of triethylantimony during OMVPE of GaAs is found, using secondary ion mass spectroscopy analysis, to increase the Zn doping concentration from <6×1018 atoms/cm3 to 9×1018 atoms/cm3, a factor of 1.6. The amount of antimony introduced into the solid is only 2–3×1017 atoms/cm3. The addition of Sb also increases the impurity concentration of In in GaAs, but does not affect the concentration of Te or P. © 2001 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Yellow and green luminescence in a freestanding GaN template

M. A. Reshchikov, H. Morkoç, S. S. Park, and K. Y. Lee

Appl. Phys. Lett. 78, 3041 (2001); http://dx.doi.org/10.1063/1.1371961 (3 pages) | Cited 22 times

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We have studied a broad photoluminescence band in high-mobility freestanding 200-μm-thick GaN template prepared by hydride vapor-phase epitaxy. Variable-excitation intensity and energy experiments showed two defect-related bands: a yellow luminescence (YL) band at about 2.15 eV and a green luminescence (GL) band at about 2.43 eV. In contrast to epitaxial GaN samples prepared by both vapor-phase and molecular-beam epitaxy, the YL in the sample studied is weak and can be easily saturated. However, the GL is dominant. We attribute the GL to isolated defects involving gallium vacancies and the YL to the same defect, but bound to dislocations, or possibly to structural surface defects. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
61.72.J- Point defects and defect clusters
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
61.72.Yx Interaction between different crystal defects; gettering effect
68.35.B- Structure of clean surfaces (and surface reconstruction)

Linear growth of thin films under the influence of stress

G. Palasantzas and J. Th. M. De Hosson

Appl. Phys. Lett. 78, 3044 (2001); http://dx.doi.org/10.1063/1.1372209 (3 pages) | Cited 3 times

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We have studied the growth of thin films in the presence of stress instability that enhances the roughness and roughening induced by conservative as well as nonconservative noise. It is clearly illustrated that nonconservative noise effects may enhance stress induced roughness. Nevertheless, the incorporation of conservative noise appears to also be substantial in growth processes driven by diffusion. For growth on a rough substrate the dependence of the amplitude of the surface roughness on the film thickness differs from that of a film growing on a flat substrate. The amplitude shows a minimum at a particular substrate thickness, which indicates that the growth up to this thickness is enforced by undulations of the substrate. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
81.15.Aa Theory and models of film growth
68.35.B- Structure of clean surfaces (and surface reconstruction)

Switchable mirrors based on nickel–magnesium films

T. J. Richardson, J. L. Slack, R. D. Armitage, R. Kostecki, B. Farangis, and M. D. Rubin

Appl. Phys. Lett. 78, 3047 (2001); http://dx.doi.org/10.1063/1.1371959 (3 pages) | Cited 138 times

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An electrochromic mirror electrode based on reversible uptake of hydrogen in nickel magnesium alloy films is reported. Thin, magnesium-rich Ni–Mg films prepared on glass substrates by co-sputtering from Ni and Mg targets are mirror-like in appearance and have low visible transmittance. Upon exposure to hydrogen gas or on cathodic polarization in alkaline electrolyte, the films take up hydrogen and become transparent. When hydrogen is removed, the mirror properties are recovered. The transition is believed to result from reversible formation of Mg2NiH4 and MgH2. A thin overlayer of palladium was found to enhance the kinetics of hydrogen insertion and extraction, and to protect the metal surface against oxidation. © 2001 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
78.66.Bz Metals and metallic alloys
42.79.Wc Optical coatings
82.45.Fk Electrodes
68.43.Mn Adsorption kinetics
82.45.Jn Surface structure, reactivity and catalysis
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Nr Association, addition, insertion, cluster formation
81.65.Kn Corrosion protection

29Si magic-angle-spinning nuclear-magnetic-resonance study of spinel-type Si3N4

T. Sekine, M. Tansho, and M. Kanzaki

Appl. Phys. Lett. 78, 3050 (2001); http://dx.doi.org/10.1063/1.1372199 (2 pages) | Cited 15 times

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29Si magic-angle-spinning nuclear-magnetic resonance has been measured on spinel-type cubic silicon nitride (c-Si3N4). c-Si3N4 shows two 29Si resonances at −50.0±0.2 and −225.0±0.2 ppm, corresponding to the tetrahedron SN4 and the octahedron SiN6, respectively. Integration of the spectrum gives SN4/SiN6 about one half that of the spinel structure. Ab initio self-consistent field Hartree–Fock molecular orbital calculations also indicate that the chemical shift for octahedral Si is more negative in nitride than in oxides. © 2001 American Institute of Physics.
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76.60.Cq Chemical and Knight shifts
61.66.Fn Inorganic compounds
61.05.Qr Magnetic resonance techniques; Mössbauer spectroscopy (for structure determination only)

Wetting layer carrier dynamics in InAs/InP quantum dots

S. Hinooda, S. Loualiche, B. Lambert, N. Bertru, M. Paillard, X. Marie, and T. Amand

Appl. Phys. Lett. 78, 3052 (2001); http://dx.doi.org/10.1063/1.1338953 (3 pages) | Cited 14 times

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The electronic coupling between InAs/InP quantum dot (QD) array and its wetting layer (WL) is studied by continuous wave and time resolved photoluminescence. The carrier dynamics is explained by the existence of two regimes in the WL: at low QD density the carrier dynamics is dominated by the diffusion and at high density when the distance between QDs is comparable to the carrier mean free path in the WL the quantum capture into QDs dominates. From the identification of these two regimes the carrier mean free path in the WL is estimated to about 30 nm. © 2001 American Institute of Physics.
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73.63.Kv Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics

Surface alignment bistability of nematic liquid crystals by orientationally frustrated surface patterns

Jong-Hyun Kim, Makoto Yoneya, Jun Yamamoto, and Hiroshi Yokoyama

Appl. Phys. Lett. 78, 3055 (2001); http://dx.doi.org/10.1063/1.1371246 (3 pages) | Cited 65 times

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We demonstrate a robust in-plane bistability of liquid-crystal surface alignment based on tailored submicrometer-sized surface domains imposing a frustrated alignment. By a nanorubbing technique utilizing the atomic force microscope, we prepared an orientational checkerboard pattern on polyimide layer, consisting of square unit domains on which the alignment is locally constrained to be planar yet orthogonal between the neighboring domains. Due to the four-fold rotational symmetry of the pattern, the two diagonal axes of the square domain become equally stable directions for the macroscopic liquid crystal alignment. The alignment could be switched between these two states by an in-plane electric field above a certain threshold, determined by the local azimuthal anchoring. © 2001 American Institute of Physics.
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61.30.-v Liquid crystals
42.70.Df Liquid crystals

Si-rich/SiO2 nanostructured multilayers by reactive magnetron sputtering

F. Gourbilleau, X. Portier, C. Ternon, P. Voivenel, R. Madelon, and R. Rizk

Appl. Phys. Lett. 78, 3058 (2001); http://dx.doi.org/10.1063/1.1371794 (3 pages) | Cited 43 times

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Silicon-rich (SR)/SiO2 multilayered systems were produced by reactive magnetron sputtering, through an approach based on the ability of hydrogen, when alternatively mixed to the argon of the plasma, to reduce the oxygen originated from the SiO2 target. Optimum values of both hydrogen partial pressure (45 mTorr) and deposition temperature (500 °C) have led to the highest incorporation of Si in the SR layer which crystallizes after annealing. The SR/SiO2 superlattices grown with such conditions showed that the size of the Si nanocrystals is limited by the thickness of the SR layer. Considering the difference observed between the photoluminescence peak position and the predicted band gap for Si nanocrystals, the results suggest that we deal with a quantum-size confinement assisted by a Si–O vibration located at the interface. © 2001 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
68.65.Cd Superlattices
73.21.Cd Superlattices
81.15.Cd Deposition by sputtering
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.35.Ja Surface and interface dynamics and vibrations
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics

Strong influence of supercooled liquid on crystallization of the Al85Ni5Y4Nd4Co2 metallic glass

Dmitri V. Louzguine and Akihisa Inoue

Appl. Phys. Lett. 78, 3061 (2001); http://dx.doi.org/10.1063/1.1371795 (3 pages) | Cited 16 times

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The present letter aims to report the effect of supercooled liquid region on crystallization behavior of an Al85Ni5Y4Nd4Co2 metallic glass produced by rapid solidification of the melt. It is found that crystallization behaviors of this alloy above and below the glass-transition temperature are completely different. Formation of the primary nanoscale α-Al particles observed during continuous heating or after annealing above glass-transition temperature does not occur during isothermal annealing below glass-transition temperature when an unidentified intermetallic compound, and α-Al phases are formed simultaneously. © 2001 American Institute of Physics.
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61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
81.30.Fb Solidification
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Dielectric exchange-force effect on the rupture force of adsorbed bilayers of self-assembled surfactant films

O. Teschke, G. Ceotto, and E. F. de Souza

Appl. Phys. Lett. 78, 3064 (2001); http://dx.doi.org/10.1063/1.1358369 (3 pages) | Cited 6 times

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We measured and formulated dielectric exchange forces between adsorbed layers of self-assembled surfactant films and atomic-force microscope tips in water. The dielectric exchange-force model is in agreement with the observation that the surfactant-layer rupture forces (tip-applied force necessary to obtain tip/substrate contact) are smaller in the thickest layers, where the compactness of the adsorbed film results in the smallest values of the dielectric permittivity. Within experimental accuracy, a dielectric permittivity value of ∼ 4 for bilayers and of ∼ 36 for monolayers is found. © 2001 American Institute of Physics.
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68.43.Fg Adsorbate structure (binding sites, geometry)
68.35.Gy Mechanical properties; surface strains
77.22.Ch Permittivity (dielectric function)
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
77.55.-g Dielectric thin films
62.20.M- Structural failure of materials
68.37.Ps Atomic force microscopy (AFM)
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Apertured quantum dot microcavity light emitting diodes

Z. Zou, H. Chen, and D. G. Deppe

Appl. Phys. Lett. 78, 3067 (2001); http://dx.doi.org/10.1063/1.1341223 (3 pages) | Cited 2 times

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Experimental data are presented showing efficiency enhancements due to size reductions of apertured quantum dot microcavity light emitting diodes. The aperture sizes are photolithographically controlled to generate four different aperture sizes that are nominally 4, 3, 2, and 1 μm diameters. Even at room temperature the efficiencies increase with decrease in aperture size. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.67.Hc Quantum dots
73.63.Kv Quantum dots
81.07.Ta Quantum dots
42.82.Cr Fabrication techniques; lithography, pattern transfer

Photoluminescence method for detecting trace levels of iron in ultrapure silicon

I. Broussell, V. A. Karasyuk, and M. L. W. Thewalt

Appl. Phys. Lett. 78, 3070 (2001); http://dx.doi.org/10.1063/1.1347018 (3 pages) | Cited 1 time

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A nondestructive technique is presented for the determination of trace levels of interstitial iron contamination in ultrapure silicon. This approach is based on the well-known ability of iron to undergo a reversible pairing reaction with boron near room temperature. A variety of float-zoned silicon samples with low concentrations of boron ( ∼ 1011 cm−3) were subjected to thermal annealing treatments to study changes in the apparent boron concentration as determined by the standard method of comparing the photoluminescence intensity of the boron bound exciton to that of the free exciton. Changes in the apparent boron concentration were attributed to the formation or dissociation of iron–boron pairs, allowing us to estimate the interstitial iron concentration in these samples. Remarkably, relatively mild thermal treatments can change the apparent boron concentration in some of these samples by up to a factor of ten. © 2001 American Institute of Physics.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
71.55.Cn Elemental semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
71.35.-y Excitons and related phenomena

Electron energy barriers between (100)Si and ultrathin stacks of SiO2, Al2O3, and ZrO2 insulators

V. V. Afanas’ev, M. Houssa, A. Stesmans, and M. M. Heyns

Appl. Phys. Lett. 78, 3073 (2001); http://dx.doi.org/10.1063/1.1366366 (3 pages) | Cited 66 times

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Electron energy barriers between the valence band of (100)Si and the conduction bands of ultrathin SiO2, Al2O3, ZrO2 insulators and their stacks were determined using internal photoemission of electrons. For SiO2, the barrier of 4.25±0.05 eV was found unchanged down to the oxide thickness of ≈1 nm. The barriers for Al2O3 and ZrO2 are substantially lower: 3.25±0.08 and 3.1±0.1 eV, respectively. Thermal oxidation at 650–800 °C enhances the barriers at the Si/Al2O3 and Si/ZrO2 interfaces but does not reduce the high density of band tail states in the insulators, suggesting the formation of silicates. © 2001 American Institute of Physics.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.At Surface states, band structure, electron density of states
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