By Topic

Applied Physics Letters

Issue 14 • Date Oct 1997

Filter Results

Displaying Results 1 - 25 of 52
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (26 KB)  
    Freely Available from IEEE
  • Bi-directional switching based on semiconductor laser/amplifier with shallow-etched bending ridge waveguide

    Page(s): 1903 - 1905
    Save to Project icon | PDF file iconPDF (773 KB)  

    A new type of optical switching device is developed. For a semiconductor laser amplifier with a shallow-etched bending ridge waveguide, the laser beam could propagate along the bending direction or the straight direction. Switching between the two directions is characterized. With the device fabricated on the substrate with two quantum wells of different widths, switching characteristics are found to significantly depend on the spectral separation of the two lasing modes. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical anisotropy of dispersed carbon nanotubes induced by an electric field

    Page(s): 1906 - 1908
    Save to Project icon | PDF file iconPDF (243 KB)  

    Carbon nanotubes dispersed in ethanol are aligned by an electric field. Due to the orientation of these elongated particles, the dispersion exhibits anisotropic behavior. Transmission experiments show rotation of the linear polarization of an incident laser beam. Alignment and relaxation times and the influence of the magnitude of the electric field have been measured. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic trapping of paramecia and estimation of their locomotive force

    Page(s): 1909 - 1911
    Save to Project icon | PDF file iconPDF (252 KB)  

    Ultrasonic trapping of locomotive organisms was studied by using paramecia of ∼0.2 mm size. An ultrasonic standing wave of ∼3 MHz was generated in a sample cell to trap the paramecia. When the ultrasonic oscillation was turned on, paramecia began to swim along the nodes of the standing wave. Furthermore, when two ultrasonic waves were crossed orthogonally in a thin sample cell, paramecia were trapped at the lattice points of the nodes. The trapping efficiency increased with the ultrasonic power density. The locomotive force of the paramecia was estimated from the threshold power density for trapping. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transition from diffusive to localized regimes in surface corrugated optical waveguides

    Page(s): 1912 - 1914
    Save to Project icon | PDF file iconPDF (86 KB)  

    Exact calculations of the transmittance of surface corrugated optical waveguides are presented. The elastic scattering of diffuse light or other electromagnetic waves from a rough surface induces a diffusive transport along the waveguide axis. As the length of the corrugated part of the waveguide increases, a transition from the diffusive to the localized regime is observed. This involves an analogy with electron conduction in nanowires, and hence, a concept analogous to that of “resistance” can be introduced. We show an oscillatory behavior of both the elastic mean-free path and the localization length versus the wavelength. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sealing of AlAs against wet oxidation and its use in the fabrication of vertical-cavity surface-emitting lasers

    Page(s): 1915 - 1917
    Save to Project icon | PDF file iconPDF (271 KB)  

    We have studied the process of sealing an exposed AlAs to prevent further wet oxidation. A critical step in this sealing process consists of the first wet oxidation for a short time at 408 °C in a steam environment of a previously room-ambient exposed AlAs surface. During this brief wet oxidation, a dense oxide surface barrier with a thickness of 1.1 μm is formed, which further blocks diffusing oxygen species during the second wet oxidation. The effectiveness of the sealing is demonstrated through its use as a mask against wet oxidation in the fabrication of oxide-confined vertical-cavity surface-emitting lasers. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Crystal growth and fabrication of a 1.3-μm-wavelength multiple-quantum-well laser on a (211)A InP substrate

    Page(s): 1918 - 1920
    Save to Project icon | PDF file iconPDF (1584 KB)  

    We demonstrate the fabrication of a long-wavelength laser on a (211) InP substrate, with the expectation of reducing threshold current density. We found that InGaAsP single quantum wells (SQWs) could be fabricated with good optical properties provided the SQW layers were not made too thin. A laser that had an unstrained multiple-quantum-well active layer emitting at 1.3 μm was fabricated on a (211)A InP substrate. Its threshold current density was 900 A/cm2, which is comparable to the value for the same type of laser on a (100) substrate. These results suggest that long-wavelength lasers with satisfactory quality can be fabricated on a (211)A substrate. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel main-chain poly-carbazoles as hole and electron transport materials in polymer light-emitting diodes

    Page(s): 1921 - 1923
    Save to Project icon | PDF file iconPDF (61 KB)  

    We report the use of substituted main-chain poly-carbazoles as hole and electron transporting polymers for electroluminescence (EL) applications. The polymers are soluble in common organic solvents and high quality thin films are obtained by spin coating method. A single layer of hole or electron transfer devices with indium tin oxide anode and aluminum cathode shows current densities up to 40–50 mA/cm2, respectively, but no visible emission from either layer. Double-layer structures combining the hole and electron transfer polymers show strong emission originated from the electron transfer layer. The peak of double-layer EL spectrum is about 30 nm redshifted to the peak of corresponding photoluminescence spectrum, which may be due to the formation of an exciplex between the two layers. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlinear optical waveguide fabrication by direct electron-beam irradiation and thermal development using a high Tg polymer

    Page(s): 1924 - 1926
    Save to Project icon | PDF file iconPDF (62 KB)  

    A nonlinear optical waveguide fabrication process for use with dye doped polymer is described. The ridge-type channel waveguide containing the chromophores was fabricated by direct electron-beam irradiation. The electron beam with an energy of 25 kV and dose of 1000 μC/cm2 was exposed directly onto the dye doped polymer film, and then thermal development and corona-poling were performed simultaneously. We could also demonstrate the periodically poled nonlinear optical polymer waveguide on the basis of this new process. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Conversion efficiency and damage threshold measurements of CsLiB6O10 with a train of laser pulses

    Page(s): 1927 - 1929
    Save to Project icon | PDF file iconPDF (201 KB)  

    The energy conversion efficiency and the damage threshold of a CsLiB6O10 crystal have been measured for a pulse train with 80 pulses at 532 nm, each with energy up to 200 μJ, 14 ps duration and 25 ns pulse to pulse spacing. Maximum energy conversion efficiency of 38% has been measured when the crystal was used to convert 532 nm to 266 nm. The damage threshold of the crystal for this pulse train was measured to be ≫130 and ≪520 GW/cm2. Both the high intensity of the micropulse and the fluence of the macropulse appear to affect the damage threshold. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Avalanche breakdown-related electroluminescence in single crystal Si:Er:O

    Page(s): 1930 - 1932
    Save to Project icon | PDF file iconPDF (55 KB)  

    Er3+-related electroluminescence (EL) at ∼1.54 μm from single-crystal silicon light-emitting diodes fabricated by erbium and oxygen co-implantation and subsequent annealing has been observed in the avalanche breakdown regime in the 80–300 K temperature range. The EL intensity decreased by a factor of 2 with a temperature increase from 80 to 300 K. The room-temperature yield under the reverse bias was over one order of magnitude higher than that under the forward bias. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Discharge impedance variations in large area radio frequency excited CO2 lasers

    Page(s): 1933 - 1935
    Save to Project icon | PDF file iconPDF (72 KB)  

    Some results from a systematic study on the impedance matching conditions and on the longitudinal power distributions in planar rf discharges for CO2 lasers, are given. They show that both plasma impedance and voltage distribution are different in cw and pulsed discharge modes revealing the importance of parameters such as the interelectrode temperature distribution and the local gas density and composition. These parameters have to be taken into account when designing matching networks and voltage smoothing schemes. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Triggering a radial multichannel pseudospark switch using electrons emitted from material with high dielectric constant

    Page(s): 1936 - 1938
    Save to Project icon | PDF file iconPDF (91 KB)  

    The electron emission from a field emission trigger unit was matched to the requirements for the simultaneous ignition of all channels in a radial multichannel pseudospark switch for a large parameter range of the pseudospark discharge. In such trigger unit the electrons are extracted from the surface of a high-ϵ material by field emission after applying a pulsed voltage. Electron emission occurs in a pressure range from 1–50 Pa, where the pseudospark discharge is operated. The access to low working gas pressures (≪10 Pa) using such trigger unit allows for achieving high hold-off voltages. The ignition of the pseudospark discharge was investigated by means of high speed photography and by a parallel observation of the electron beam of a single discharge channel, which occurs in hollow-cathode phase. © 1997 American Institute of Physics.   View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High power switching behavior in electrically conductive polymer composite materials

    Page(s): 1939 - 1941
    Save to Project icon | PDF file iconPDF (46 KB)  

    The electrical switching properties of electrically conductive polymer composites are studied at high current densities. It is shown that the switching properties at high current densities are substantially different from those at low current densities which depend on a positive temperature coefficient of resistance effect. This type of switching appears to be a general feature of conductor-filled polymer composite materials and should lead to a new class of fast, current-limiting devices for power circuits. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ion mass effect in plasma-induced charging

    Page(s): 1942 - 1944
    Save to Project icon | PDF file iconPDF (103 KB)  

    Simulations of charging and profile evolution during etching of high aspect ratio polysilicon gates in typical high-density plasmas containing heavy ions (e.g., BCl3+, Cl2+), predict a reduction in charging and notching when lighter ions (e.g., He+) are added. The reduction occurs because of the influence of the ion mass on the ratio R of the ion sheath transit time to the rf period, which determines the spread in the ion energy distribution at the wafer. The effect is most pronounced when R≤0.1–0.2 for light ions and, simultaneously, R≥0.6 for heavy ions; then, more light ions arrive at the patterned structure with low energies, where they help decrease localized charging. When the rf bias frequency is reduced so that R≤0.3 for all ions, the effect disappears. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation of current transients through ultrathin gate oxides during plasma etching

    Page(s): 1945 - 1947
    Save to Project icon | PDF file iconPDF (128 KB)  

    Monte Carlo simulations of electron tunneling through a 3 nm gate oxide during etching of dense patterns of gate electrodes in uniform high-density plasmas reveal two current transients, which occur: (a) when the open area clears, and (b) when the polysilicon lines just become disconnected at the bottom of trenches. The first charging transient is fast (controlled by charging) and may be followed by a steady-state current which lasts until the lines get disconnected. The second charging transient lasts longer; the magnitude of the tunneling current generally decreases as the sloped polysilicon sidewalls become straighter. Most of the damage occurs at the edge gate when the open areas are covered by field oxide; however, the edge gate suffers no damage when the 3 nm oxide extends into the open areas. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formation of diamond in carbon onions under MeV ion irradiation

    Page(s): 1948 - 1950
    Save to Project icon | PDF file iconPDF (522 KB)  

    Spherical carbon onions are generated by irradiating graphitic carbon soot with Ne+ ions of 3 MeV energy. Under continued irradiation, a transformation of their cores to cubic diamond crystals is observed. In comparison to earlier electron irradiation experiments, the yield of diamond is much higher. The output of the irradiation experiment is characterized by electron microscopy and electron energy loss spectroscopy. Knock-on displacements of carbon atoms by Ne+ ions are assumed to be responsible for a self-compression of the onions, leading to the nucleation of diamond in their cores. The increased diamond yield is explained by the higher displacement cross-section, the higher energy transfer, and the higher total beam current on the specimen. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Roughness improvement and hardness enhancement in nanoscale Al/AlN multilayered thin films

    Page(s): 1951 - 1953
    Save to Project icon | PDF file iconPDF (900 KB)  

    Al/AlN multilayered thin films with periodic thickness λ less than 24 nm were developed by ion beam assisted deposition. A considerably small surface roughness comparable to that of the silicon substrate and much smaller than those of both monolithic Al and AlN films was obtained. Over the investigated range of λ, all the multilayers are harder than the homogeneous AlN film, and a significant hardness enhancement by a factor of ∼2 over that of the AlN film was observed in the multilayer with λ of 6 nm. Moreover, the hardness enhancement is not at the expense of the multilayer toughness, with the multilayer Al/AlN films showing improved plasticity as compared with the AlN film. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal oxide growth at chemical vapor deposited SiO2/Si interface during annealing evaluated by difference x-ray reflectivity

    Page(s): 1954 - 1956
    Save to Project icon | PDF file iconPDF (75 KB)  

    The x-ray interference technique has been applied to evaluate the structural changes of high temperature grown chemical vapor deposited (CVD) SiO2 film under several post annealing conditions. In annealing above 800 °C in O2 ambient, a thermal oxide growth has been found at the CVD SiO2/Si interface, and its precise thicknesses have been determined. The estimated diffusion coefficient of the oxidant in CVD film was about three times larger compared to that of thermal oxide. A threshold voltage shift in the oxide was found to strongly correlate to the thickness of the thermal oxide rather than to thermal modifications of the CVD SiO2 itself. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nondestructive assessment of the grain size distribution of SnO2 nanoparticles by low-frequency Raman spectroscopy

    Page(s): 1957 - 1959
    Save to Project icon | PDF file iconPDF (353 KB)  

    A nondestructive methodology is reported to obtain the grain size distribution of SnO2 nanoparticles, with grain sizes below 10 nm, using low-frequency Raman scattering measurements. The position of the main low-frequency Raman bands depends on the grain size and can be correlated with the spheroidal vibration modes of a spherical elastic body with “rigid” boundaries. The grain size distributions deduced from Raman scattering are in agreement with the direct measurements from transmission electron microscopy, especially for the smaller grains. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Near-field scanning optical microscopy of ferroelectric domain walls

    Page(s): 1960 - 1962
    Save to Project icon | PDF file iconPDF (149 KB)  

    We have observed domain walls in ferroelectric LiTaO3 crystals using a polarization and phase sensitive near-field scanning optical microscope. The strain induced birefringence was used to observe the domain walls. The domain walls are measured to be 1 μm wide and show a variation of strain along the domain walls probably due to defects. These measurements allow an estimate of the birefringence at the domain wall of 6×10-5 and associated shear strain of 4×10-5. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Increased radiative lifetime of rare earth-doped zinc oxyhalide tellurite glasses

    Page(s): 1963 - 1965
    Save to Project icon | PDF file iconPDF (68 KB)  

    We have investigated the structural and optical properties of rare earth-doped zinc tellurite glasses modified by the substitution of ZnF2. Raman and phonon sideband spectroscopies were employed to characterize changes in the glass structure as well as to probe vibrational behavior in the immediate vicinity of the rare earth ion. These measurements are combined with photoluminescence and optical absorption to monitor the effect of halide substitution upon the optical behavior of the rare earth dopant. A substantial increase in the intrinsic radiative lifetime of Nd3+ is observed with increasing halide concentration. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parallel epitaxy of TiN(100) thin films on Si(100) produced by pulsed reactive crossed-beam laser ablation

    Page(s): 1966 - 1968
    Save to Project icon | PDF file iconPDF (469 KB)  

    TiN(001)[100]∥Si(001)[100] parallel epitaxy of thin films grown by pulsed reactive crossed-beam laser ablation (KrF, 248 nm) is investigated in situ by reflection high-energy electron diffraction and ex situ by x-ray diffraction, full-hemispherical X-ray photoelectron diffraction and low-energy electron diffraction. TiN films are grown on atomically flat, initially two domain 2×1 reconstructed Si(001) surfaces at 100≤T≤800° C. Parallel epitaxy is found to prevail at T≥400 °C with growth rates in the 10-2 monolayer/pulse-1 range and a repetition rate of 2 Hz. The substrate and film morphologies are investigated using atomic force microscopy. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduced bias growth of pure-phase cubic boron nitride

    Page(s): 1969 - 1971
    Save to Project icon | PDF file iconPDF (123 KB)  

    We report results on an improved growth process for cubic boron nitride (c-BN) films. The films are deposited on a dc-biased silicon substrate using ion-assisted sputtering. First, we grow a BN template layer at a bias voltage which maximizes the sp3 content. After this template layer attains a thickness of ∼500 Å, corresponding to the coalescence of the mosaiclike grain structure, we find that we can reduce the substrate bias to about 50% of its initial value while sustaining pure phase c-BN growth. The reduction in nitrogen ion energy results in a dramatic increase in the growth rate as well as significantly improved film quality. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low-dimensional structures generated by misfit dislocations in the bulk of Si1-xGex/Si heteroepitaxial systems

    Page(s): 1972 - 1974
    Save to Project icon | PDF file iconPDF (212 KB)  

    The capability of misfit dislocations to generate nanostructures in the bulk of Si1-xGex/Si heteroepitaxial systems is demonstrated. It is shown that dislocation slip originating from compositionally graded Si1-xGex layers can produce a range of low-dimensional structures including nanowires, nanodots, and mosaic superlattices. Formation of the nanostructures is achieved in parallel processing, through a simple two-step cycle which includes growth of layered planar structures and postgrowth annealing. © 1997 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

Full Aims & Scope

Meet Our Editors

Editor
Nghi Q. Lam
Argonne National Laboratory