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8 Oct 2001

Volume 79, Issue 15, pp. 2309-2491

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Opal-like photonic crystal with diamond lattice

F. García-Santamaría, C. López, F. Meseguer, F. López-Tejeira, J. Sánchez-Dehesa, and H. T. Miyazaki

Appl. Phys. Lett. 79, 2309 (2001); http://dx.doi.org/10.1063/1.1406560 (3 pages) | Cited 20 times

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A method to fabricate a diamond structure with a complete photonic bandgap in the near infrared is proposed. The procedure starts by building an opal with body-centered-cubic symmetry composed of two types (organic and inorganic) of microspheres by means of a microrobotic technique. Then, the organic particles may be selectively removed to obtain a diamond structure of inorganic particles. This method can be extended to make diamond inverse opals of silicon with full gap to midgap ratios as large as 13% for moderate filling fractions. © 2001 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.16.-c Methods of micro- and nanofabrication and processing
81.20.-n Methods of materials synthesis and materials processing
42.50.-p Quantum optics
42.70.Qs Photonic bandgap materials
06.60.Sx Positioning and alignment; manipulating, remote handling

Group velocity and propagation losses measurement in a single-line photonic-crystal waveguide on InP membranes

X. Letartre, C. Seassal, C. Grillet, P. Rojo-Romeo, P. Viktorovitch, M. Le Vassor d’Yerville, D. Cassagne, and C. Jouanin

Appl. Phys. Lett. 79, 2312 (2001); http://dx.doi.org/10.1063/1.1405146 (3 pages) | Cited 65 times

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Single-line photonic-crystal waveguides are investigated. Photoluminescence experiments and three-dimensional calculation are performed and allow a clear identification of the guided modes. The propagation properties of the latter (group velocity, losses) are extracted from photoluminescence spectra obtained on closed waveguides which act as linear cavities. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.82.Et Waveguides, couplers, and arrays
78.55.-m Photoluminescence, properties and materials

Impact of texture-enhanced transmission on high-efficiency surface-textured light-emitting diodes

R. Windisch, C. Rooman, S. Meinlschmidt, P. Kiesel, D. Zipperer, G. H. Döhler, B. Dutta, M. Kuijk, G. Borghs, and P. Heremans

Appl. Phys. Lett. 79, 2315 (2001); http://dx.doi.org/10.1063/1.1397758 (3 pages) | Cited 56 times

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The transmission properties of semiconductor surfaces can be changed by surface texturing. We investigate these changes experimentally and find that an enhancement of the angle-averaged transmission by a factor of 2 can be achieved with optimum texturing parameters. This enhanced transmission provides an additional light extraction mechanism for high-efficiency surface-textured light-emitting diodes. External quantum efficiencies of 46% and 54% are demonstrated before and after encapsulation, respectively. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.68.+m Optical properties of surfaces
78.66.Fd III-V semiconductors

Spectroscopic analysis and persistent photon-gated spectral hole burning in LiF:F2− color center crystal

V. V. Fedorov, S. B. Mirov, M. Ashenafi, and L. Xie

Appl. Phys. Lett. 79, 2318 (2001); http://dx.doi.org/10.1063/1.1406563 (3 pages) | Cited 3 times

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Luminescence and absorption spectra of LiF crystals with F2− color centers (CCs) were studied in the 14–300 K temperature range. The Huang–Rhys factors measured from absorption and emission spectra were equal in magnitude and calculated to be 3.2 and 2.72 at 77 and 300 K, respectively. It was shown that below 40 K inhomogeneous broadening of the zero phonon line of the F2− CC prevails over homogeneous broadening. Inhomogeneous broadening of the zero phonon line was observed to vary from 5 to 15 cm−1 for different crystal preparations. Persistent spectral hole burning stable at room temperature was realized in LiF:F2− crystals. © 2001 American Institute of Physics.
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61.72.J- Point defects and defect clusters
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.40.Ha Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials

Single sharp spot in fluorescence microscopy of two opposing lenses

C. M. Blanca, J. Bewersdorf, and S. W. Hell

Appl. Phys. Lett. 79, 2321 (2001); http://dx.doi.org/10.1063/1.1407303 (3 pages) | Cited 21 times

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We demonstrate theoretically, experimentally, and in an imaging application the possibility to generate a single predominant sharp diffraction maximum in the effective point-spread function of a fluorescence microscope that coherently uses two opposing lenses. This is achieved through binary pupil filters that preclude the origination of the unfavorable strong interference side maxima that are otherwise present in these systems. Mathematical postprocessing, which has so far been a prerequisite to gain artifact-free images, is now optional or obsolete. © 2001 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
07.60.Pb Conventional optical microscopes

Multiwavelength laterally complex coupled distributed feedback laser arrays with monolithically integrated combiner fabricated by focused-ion-beam lithography

L. Bach, I. P. Reithmaier, A. Forchel, J. L. Gentner, and L. Goldstein

Appl. Phys. Lett. 79, 2324 (2001); http://dx.doi.org/10.1063/1.1392977 (3 pages) | Cited 4 times

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A multiwavelength laser array with four complex coupled distributed feedback lasers was fabricated by focused-ion-beam lithography. The laser array was monolithically integrated with a combiner network to allow simultaneous operation and coupling of four wavelengths into one single-mode fiber. To reduce the fabrication complexity, focused-ion-beam technology was used to define complex coupled gratings lateral to pumped ridge waveguide sections without any further overgrowth step. A four wavelength output with 6-nm-wavelength spacing and side-mode suppression ratios of more than 35 dB were obtained with output powers up to 6 mW per channel. © 2001 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.81.Qb Fiber waveguides, couplers, and arrays
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Et Waveguides, couplers, and arrays

Linear optical properties of Ge nanocrystals in silica

Annette Dowd, Robert G. Elliman, and Barry Luther-Davies

Appl. Phys. Lett. 79, 2327 (2001); http://dx.doi.org/10.1063/1.1409591 (3 pages) | Cited 2 times

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The absorption and extinction spectra of Ge nanocrystals in silica formed by ion implantation are studied using photothermal deflection and transmission spectroscopies. It is found that scattering makes a significant contribution to the extinction spectrum, damping the spectral features and resulting in a Rayleigh scattering-like ω4 dependence. In contrast, the spectra measured by photothermal deflection clearly show features such as the E1/E1+Δ1 transitions. The Tauc gap is extracted to be ∼ 0.7±0.1 eV. © 2001 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.30.Am Elemental semiconductors and insulators
61.72.up Other materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors
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Coulomb correction effects on bremsstrahlung spectra from non-Maxwellian plasmas

Young-Dae Jung

Appl. Phys. Lett. 79, 2330 (2001); http://dx.doi.org/10.1063/1.1409334 (3 pages) | Cited 4 times

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Coulomb correction effects are investigated on electron–ion bremsstrahlung emission from a non-Maxwellian velocity distribution plasma of the form exp[−(ν/νm)m] where νm2 = (3kBTe/Me)Γ(3/m)/Γ(5/m) and 2 ⩽ m ⩽ 5. The bremsstrahlung emission rate is obtained as a function of the photon energy. For soft photon radiations, the Coulomb correction effects on the bremsstrahlung emission rate are found to be more significant for the distribution with m = 2, i.e., Maxwellian distribution plasmas. However, for hard photon radiations, the Coulomb correction effects are found to be almost independent of the non-Maxwellian character. Thus, it would be possible to figure out the form of the electron distribution function using hard bremsstrahlung spectra rather than soft bremsstrahlung spectra since the bremsstrahlung emission rate without the Coulomb corrections only depends on the non-Maxwellian character for hard photon radiations. © 2001 American Institute of Physics.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.La X-ray and γ-ray measurements

Evanescent wave absorption by Xe(1s5) lying on a discharge tube wall

M.-A. Bratescu, Y. Sakai, and T. Kamada

Appl. Phys. Lett. 79, 2333 (2001); http://dx.doi.org/10.1063/1.1409274 (3 pages) | Cited 1 time

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A simple and sensitive detection method of Xe(1s5) excited atoms in the vicinity of a discharge wall with laser-collision induced fluorescence (LCIF) produced by evanescent wave absorption is proposed. The signal to noise (S/N) ratio was 102. The hyperfine structure (hfs) in the Xe LCIF spectra induced by resonant absorption of Xe(1s5→2p6) was confirmed to be identical with the hfs in laser absorption spectra, although the detection point (xPD) on the discharge wall was chosen independently of the position of the EW absorption (xEW). The insignificantly large fluorescence, which appeared for incident light angles to a prism larger than 4.8°, is explained by the fact that the refracted light emerged in a plasma. The Xe(1s5) number density in a dc Xe discharge, although roughly estimated, on the tube wall between the electrodes is presented. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
32.50.+d Fluorescence, phosphorescence (including quenching)
52.80.-s Electric discharges
32.30.Rj X-ray spectra
31.15.vj Electron correlation calculations for atoms and ions: excited states

Influence of laser intensity and pulse duration on the extreme ultraviolet yield from a water jet target laser plasma

U. Vogt, H. Stiel, I. Will, P. V. Nickles, W. Sandner, M. Wieland, and T. Wilhein

Appl. Phys. Lett. 79, 2336 (2001); http://dx.doi.org/10.1063/1.1406140 (3 pages) | Cited 21 times

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Extreme ultraviolet (EUV) emission in the 11–15 nm wavelength range from a thin liquid water jet target under illumination with a high repetition rate, high average power laser (Nd-YLF) has been studied. To find the optimum conversion efficiency of laser light into EUV radiation, different laser parameters were applied. The laser intensity was varied between 1011 and 1015 W/cm2, and pulse duration in the range from 30 ps to 3 ns. A maximum conversion efficiency of 0.12% in 2.2% bandwidth and 4π steradian at 13 nm was achieved at a repetion rate of 250 kHz, and a strong dependence of the conversion efficiency on both laser intensity and pulse duration was found. © 2001 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.75.-d Plasma devices
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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Nitrogen pairs, triplets, and clusters in GaAs and GaP

P. R. C. Kent and Alex Zunger

Appl. Phys. Lett. 79, 2339 (2001); http://dx.doi.org/10.1063/1.1408275 (3 pages) | Cited 17 times

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The electronic and atomic structure of substitutional nitrogen pairs, triplets, and clusters in GaP and GaAs is studied using the multiband empirical pseudopotential method with atomistically relaxed supercells. A single nitrogen impurity creates a localized a1(N) gap state in GaP, but in GaAs, the state is resonant above the conduction-band minimum. We show how the interaction of multiple a1 impurity levels, for more than one nitrogen, results in a nonmonotonic relationship between energy level and impurity separation. We assign the lowest (NN1) line in GaP to a [2,2,0] oriented pair, the second (NN2) line to a triplet of nitrogen atoms, and identify the origin of a deeper observed level as an [1,1,0] oriented triplet. We also demonstrate that small nitrogen clusters readily create very deep levels in both GaP and GaAs. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Role of bond coordination and molecular volume on the dielectric constant of mixed-oxide compounds

H. A. Kurtz and R. A. B. Devine

Appl. Phys. Lett. 79, 2342 (2001); http://dx.doi.org/10.1063/1.1409590 (3 pages) | Cited 1 time

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First-principles calculations have been employed to study clusters of Zr embedded in SiO2. Stable complexes are found with four, six, and seven oxygens coordinated to the Zr atom. Consistent with experiment, the higher coordinated complexes are the most stable. These also have a higher density, and hence, smaller molar volume. This smaller molar volume provides an explanation of the increased dielectric constant of ZrxSi1−xO2 mixed-oxide systems for small amounts of Zr (x<0.3). An unusual sevenfold coordinated structure is described. © 2001 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
61.50.Lt Crystal binding; cohesive energy
61.66.Fn Inorganic compounds
71.15.Nc Total energy and cohesive energy calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
68.47.Jn Clusters on oxide surfaces

Electronic transport in Cd–Yb and Y–Mg–Zn quasicrystals

A. L. Pope, T. M. Tritt, R. Gagnon, and J. Strom-Olsen

Appl. Phys. Lett. 79, 2345 (2001); http://dx.doi.org/10.1063/1.1406555 (3 pages) | Cited 25 times

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Electronic transport properties of the stable binary Cd5.7Yb quasicrystal and a quasicrystal in the Y–Mg–Zn family is presented. Electrical conductivity in these systems is an order of magnitude higher than other quasicrystals, resulting in larger thermal conductivity values due to enhanced electronic contributions (λE = L0σT). Room temperature Hall measurements provide a charge carrier density of 2.3×1021 and 3.1×1020 cm−3 in Cd5.7Yb and Y–Mg–Zn, respectively, indicating these materials have a higher carrier concentration and are better conductors than other quasicrystalline counterparts. Thermoelectric power in both Cd5.7Yb and Y–Mg–Zn have relatively small magnitudes (16 and 8 μV/K, respectively). Despite many similarities between these two systems, low temperature specific heat reveals a low Debye temperature in Cd5.7Yb(140 K) while the Debye temperature of Y–Mg–Zn and other quasicrystals is at least twice as large. Consequences of the electrical transport in these systems will be discussed. © 2001 American Institute of Physics.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
65.40.Ba Heat capacity
72.15.Gd Galvanomagnetic and other magnetotransport effects
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Modulating fluorescence of 8-quinolinolato compounds by functional groups: A theoretical study

Manabu Sugimoto, Masaharu Anzai, Kei Sakanoue, and Shigeyoshi Sakaki

Appl. Phys. Lett. 79, 2348 (2001); http://dx.doi.org/10.1063/1.1408278 (3 pages) | Cited 18 times

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Substituent dependence of a fluorescence energy of the 8-quinolinolato anion (Q−) was systematically investigated with electronic structure calculations. Large red- and blueshifts of the fluorescence were predicted for Q− with the NO2 and CN groups, respectively. For bis(8-quinolinolato)berylium with the NO2 and CN groups, the emission energies were calculated to be 1.56 eV (795 nm) and 2.66 eV (466 nm), respectively, indicating that they are potential candidates as red- and blue-light-emitting compounds. © 2001 American Institute of Physics.
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78.55.Kz Solid organic materials
33.50.Dq Fluorescence and phosphorescence spectra
31.15.bu Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.)
71.20.Rv Polymers and organic compounds
31.15.vq Electron correlation calculations for polyatomic molecules

Degenerate four-wave-mixing spectroscopy on epitaxially laterally overgrown GaN: Signals from below the fundamental absorption edge

Kunimichi Omae, Yoichi Kawakami, Shigeo Fujita, Yukihiro Kiyoku, and Takashi Mukai

Appl. Phys. Lett. 79, 2351 (2001); http://dx.doi.org/10.1063/1.1407298 (3 pages) | Cited 5 times

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We performed photoluminescence (PL) and degenerate four-wave-mixing (FWM) spectroscopy in epitaxially laterally overgrown GaN at 10 K. Optical transitions based on exciton complexes such as biexciton emission, exciton–exciton scattering, electron–hole plasma, and so on, were revealed by PL under a wide range of excitation densities. The FWM signals were observed from states below the fundamental excitonic absorption edge, showing that nonlinear photoswitching can be performed with a transmittance geometry. The origin of such nonlinearlity was discussed by correlating with feasible many-body effects between excitons, biexcitons, and free carriers. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.55.Cr III-V semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

In situ threshold photoemission yields correlated to surface reconstructions of InAs (001)

J. J. Zinck, R. S. Ross, J. H. G. Owen, W. Barvosa-Carter, F. Grosse, and C. Ratsch

Appl. Phys. Lett. 79, 2354 (2001); http://dx.doi.org/10.1063/1.1406552 (3 pages) | Cited 3 times

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Threshold photoemission yields for As and In terminated reconstructions of InAs (001) are measured in situ and the variation of the photoyield is correlated with the surface stoichiometry. A significant excess in the measured photoelectron yield is found for the In terminated surfaces. These results are compared to a semiempirical model based on density-functional theory calculations of the surface local densities of states for the As terminated β2-(2×4) and newly predicted ζ-(4×2) reconstructions. The calculations are in good agreement with the measured trends, and provide a basis for the interpretation of threshold photoemission sensor signatures. © 2001 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.66.Bi Elemental solids
61.66.Dk Alloys
73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Atomic force microscopy inspection of the early state of formation of polymer surface relief gratings

O. Henneberg, Th. Geue, M. Saphiannikova, U. Pietsch, L. F. Chi, P. Rochon, and A. L. Natansohn

Appl. Phys. Lett. 79, 2357 (2001); http://dx.doi.org/10.1063/1.1409584 (3 pages) | Cited 13 times

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The process of surface relief grating formation was inspected by atomic force microscopy after short-pulse exposure with counter-rotating circularly polarized laser light of 488 nm on a polymer film containing an azobenzene side-chain homopolymer (pDR1M, TG = 129 °C). During light inscription, the grating formation was probed by time-resolved visible scattering with red laser light. The efficiency of grating formation depends on the pulse length of blue light exposure. The shortest pulse length of 2 s did not create a permanent surface relief. After 5 s, a speckled surface modification starts rising and the surface relief becomes more and more uniform with a sinusoidal shape for longer exposure. The experimental findings reveal the individual addressing of azobenzene side groups by the actinic light providing a local lateral force via molecular trans-cis and cis-trans isomerization which subsequently causes grating formation. © 2001 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.70.Jk Polymers and organics
68.37.Ps Atomic force microscopy (AFM)
68.47.Mn Polymer surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)

Effect of initial states on the phase diagram of the structural pattern in magnetic fluid films under perpendicular magnetic field

Chin-Yih Hong, C. A. Chen, Chun-Hui Chen, H. E. Horng, S. Y. Yang, and H. C. Yang

Appl. Phys. Lett. 79, 2360 (2001); http://dx.doi.org/10.1063/1.1409272 (3 pages) | Cited 7 times

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When a magnetic fluid thin film is subjected to a magnetic field perpendicular to the plane of the film, a portion of magnetic particles is condensed out from the initially monodispersed magnetic fluid and forms magnetic columns. These columns evolve from a disordered column phase to a two-dimensional ordered structural pattern as the field strength reaches some critical value, Hh. The structural pattern formative process of the ordered structures that follows depends on the condition of the disordered column phase. In the letter, the effect of the initial disordered column phase, which can be altered by changing the initial field strength, Hi, on the formative process of the ordered structures is studied, and a phase diagram on the H–Hi plane is constructed. With an initial field strength that exceeds Hh, the structural pattern formative process goes through a plateau, a transition phase, and another plateau. On the other hand, if the initial field strength is less than Hh, the columns in the disordered column phase split and new columns emerge in the magnetic fluid film as the field strength increases. Finally, the structural pattern reaches a plateau. In both processes, the distance between columns in the structural patterns converges to that of a pseudostatic case. © 2001 American Institute of Physics.
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75.50.Mm Magnetic liquids
64.70.Ja Liquid-liquid transitions
82.70.Dd Colloids

Scanning x-ray microtopographs of misfit dislocations at SiGe/Si interfaces

P. M. Mooney, J. L. Jordan-Sweet, and S. H. Christiansen

Appl. Phys. Lett. 79, 2363 (2001); http://dx.doi.org/10.1063/1.1408601 (3 pages)

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Misfit dislocations at Si1−xGex/Si interfaces have been imaged by x-ray microdiffraction using the 004 diffraction peak of both the Si1−xGex layer and the Si(001) substrate. At the Si1−xGex layer peak, a decrease in the diffracted intensity is found at dislocations, with features as narrow as 4 μm. Similar features are seen using the Si peak; however, the diffracted intensity increases at the dislocations. We discuss the intensity contrast mechanisms and demonstrate that the distortion of the crystal lattice from the dislocations extends throughout the entire epitaxial layer structure. © 2001 American Institute of Physics.
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68.65.Ac Multilayers
68.37.Yz X-ray microscopy
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Stress relaxation effect in porous 3C-SiC/Si heterostructure by micro-Raman spectroscopy

V. Lysenko, D. Barbier, and B. Champagnon

Appl. Phys. Lett. 79, 2366 (2001); http://dx.doi.org/10.1063/1.1409278 (3 pages) | Cited 8 times

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Cubic (3C) SiC layers with initial biaxial stress value of about 0.4 GPa are observed by micro-Raman scattering measurements to be completely relaxed after formation of a porous network in the 3C-SiC/Si heterostructure. The porous heterostructure is obtained by an anodization procedure in HF acid solutions usually used for porous Si fabrication. The influence of some anodization parameters such as the anodization current density, HF concentration, and anodization depth on the stress relaxation effect is described. The relaxation is found to be mainly due to pore formation at the 3C-SiC/Si interface. © 2001 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.05.Rm Porous materials; granular materials
78.30.Hv Other nonmetallic inorganics
81.05.Hd Other semiconductors
78.66.Li Other semiconductors

Near-field ultraviolet photoluminescence spectroscopy for evaluating the crystallinity of polycrystalline zinc oxide

T. Yatsui, T. Shimizu, Y. Yamamoto, M. Kourogi, M. Ohtsu, and G. H. Lee

Appl. Phys. Lett. 79, 2369 (2001); http://dx.doi.org/10.1063/1.1410357 (3 pages) | Cited 6 times

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By extending the optical near-field technique to the ultraviolet region, a two-dimensional evaluation of the optical properties and crystallinity of polycrystalline zinc oxide (ZnO) was carried out at room temperature. Using an ultraviolet fiber probe with an aperture diameter of 80 nm, we obtained spatially resolved photoluminescence spectra from individual ZnO nanocrystallites; the emission intensity depended on the topography and on crystal orientation. © 2001 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Origin of field-dependent optical transmission of magnetic fluid films

S. Y. Yang, Y. P. Chiu, B. Y. Jeang, H. E. Horng, Chin-Yih Hong, and H. C. Yang

Appl. Phys. Lett. 79, 2372 (2001); http://dx.doi.org/10.1063/1.1410331 (3 pages) | Cited 40 times

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The physical mechanism of the optical transmission of magnetic fluid films under perpendicular magnetic fields is investigated in this work. Under perpendicular magnetic fields, originally dispersed magnetic particles agglomerate to form magnetic columns. The liquid phase is transparent, whereas the columns are opaque. Hence, the liquid phase dominates the optical transmission of the magnetic fluid film. When the field strength is raised, more columns are formed, and the area of the liquid phase is reduced. This leads to the decrease in the optical transmission of the film under higher field strength. The variation in the concentration of the liquid phase under various field strengths also contributes to the transmission of the film. By taking account of the variations of the effective concentration and the area ratio of the liquid phase in the magnetic fluid film under magnetic fields, the resultant magnetic field dependence of the optical transmission was calculated and found to be consistent with the experimental results. This provides evidence for the origin of the field-dependent optical transmission of the magnetic fluid film under external fields. © 2001 American Institute of Physics.
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68.15.+e Liquid thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
78.20.Ls Magneto-optical effects
75.50.Mm Magnetic liquids
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Structural phase transition as a mechanism for broadband, low-threshold reflectivity switching in gallium

K. F. MacDonald, V. A. Fedotov, N. I. Zheludev, B. V. Zhdanov, and R. J. Knize

Appl. Phys. Lett. 79, 2375 (2001); http://dx.doi.org/10.1063/1.1409335 (3 pages) | Cited 8 times

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We report that a nanoscale laser-induced structural phase transition involving just a few nanometers of gallium at an interface with silica can drive reversible changes in the optical properties of the interface in a very broad spectral range from 440 to 680 nm and beyond. At temperatures up to 15° below the melting point of gallium (30 °C) 3 ns excitation pulses, with fluences of just a few mJ/cm2, are sufficient to induce reflectivity increases of up to 40%. © 2001 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
68.35.Rh Phase transitions and critical phenomena
78.68.+m Optical properties of surfaces
64.70.K- Solid-solid transitions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Evidence for the precursors of nitrided silicon in the early stages of silicon oxynitridation in N2:N2O atmosphere

G. F. Cerofolini, M. Camalleri, C. Galati, S. Lorenti, L. Renna, O. Viscuso, G. G. Condorelli, and I. L. Fragalà

Appl. Phys. Lett. 79, 2378 (2001); http://dx.doi.org/10.1063/1.1404133 (3 pages) | Cited 8 times

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Nitridation of hydrogen-terminated silicon with N2:N2O has been studied by x-ray photoemission spectroscopy. Our analysis has given evidence that the broad N(1s) peak at 398–399 eV, usually reported in the literature, is preceded by the formation of a narrow peak at 397.5 eV, attributed to the moiety Si3N in which silicon is only marginally oxidized, and two other peaks at 400.0 eV and 401.5 eV, attributed to the moieties Si2NOSi and SiNO, respectively. © 2001 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.05.Cy Elemental semiconductors
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Charge carrier response time in sputtered a-C/n-Si heterojunctions

N. Konofaos, C. T. Angelis, E. K. Evangelou, C. A. Dimitriadis, and S. Logothetidis

Appl. Phys. Lett. 79, 2381 (2001); http://dx.doi.org/10.1063/1.1404403 (3 pages) | Cited 8 times

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Amorphous carbon (a-C)/n-Si heterojunctions were developed by rf magnetron sputtering from a carbon target on Si(100) n-type substrates kept at room temperature. Subsequent metallization by the deposition of sputtered TiN on top of the carbon films resulted in the creation of effective heterojunction devices as shown by electrical characterization. The electrical performance of the devices was further investigated by admittance spectroscopy, allowing the calculation of the charge carrier response time which was found to be of the order of 10−6 s at room temperature, the lower value reported so far when compared to similar values reported for chemically vapor deposited films. These results showed that the devices were suitable for use in fast electronics working in hard environments. © 2001 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Jc Amorphous semiconductors; glasses
81.15.Cd Deposition by sputtering
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Cw Elemental semiconductors
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