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Applied Physics Letters

Issue 19 • Date Nov 1988

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Displaying Results 1 - 25 of 35
  • Linear and nonlinear optical properties of 2‐(N‐prolinol)‐5‐nitropyridine

    Page(s): 1779 - 1781
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    The optical and nonlinear optical properties of 2‐(N‐prolinol)‐5‐nitropyridine (PNP) have been investigated. The refractive indices show strong dispersion and high birefringence in the spectral range from 488 to 1064 nm. At 632 nm the main refractive indices are nx=1.990, ny=1.788, and nz=1.467. The two major nonlinear optical susceptibilities were determined (dyxx=48 pm/V, dyyy=17 pm/V). Angle‐tuned phase‐matched second‐harmonic generation was demonstrated at 1064 nm. Type I noncritical phase matching using the nonlinear optical susceptibility dyxx is predicted for a fundamental wavelength λ=1020 nm. View full abstract»

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  • Waveguiding in spun films of soluble polydiacetylenes

    Page(s): 1782 - 1784
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    In prism coupling experiments, the guiding of 1.06 μm light over 3 cm pathlengths was demonstrated in thin spun films of soluble polydiacetylenes. From measurements of the intensity of scattered light, we estimate the transmission losses in the films were as low as 1 dB/cm. Although spun films appeared isotropic when examined under polarized light, the coupling angle observed for the TM waveguide mode was ∼6° higher than that of the TE mode, implying that the films were istropic in the plane of the film, but the refractive index normal to the plane of the film was lower. View full abstract»

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  • Bistable switching in nonlinear Al0.06Ga0.94As étalons

    Page(s): 1785 - 1787
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    Optical bistability at 5 mW input power at 840 nm is reported in Al0.06Ga0.94As étalons grown by metalorganic vapor phase epitaxy, having an epitaxially grown high‐reflecting back mirror. The devices have been switched from the high‐reflecting to the low‐reflecting state with pulses from a laser diode operating at 778 nm with 10 pJ switching energy. The devices could be thermally stable for as long as 200 μs. The experimental results are compared with a simple theoretical model. View full abstract»

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  • Measurement of high‐order optical nonlinear susceptibilities in semiconductor‐doped glasses

    Page(s): 1788 - 1790
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    The optical susceptibilities of CdSxSe1-x ‐doped glasses were observed up to χ(11) using a spatially resolved phase‐matched multiwave mixing technique. Using a pulsed dye laser tuned near the band gap, measurements were performed for ∥χ(3)∥, ∥χ(5)∥, and ∥χ(7)∥ in four different commercial filter glasses. View full abstract»

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  • Picosecond all‐optical switching in single‐mode GaAs/AlGaAs strip‐loaded nonlinear directional couplers

    Page(s): 1791 - 1793
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    Room‐temperature all‐optical switching has been achieved in single‐mode strip‐loaded nonlinear directional couplers with a GaAs/AlGaAs multiple quantum well guiding layer. For low input intensities nearly complete (1:3–1:5) cross coupling occurs, while at high input intensities switching occurs so that most (≫3:1) of the light stays in the input guide. The effects of carrier diffusion are minimized by the use of picosecond pulses. The response time and the recovery time of the nonlinear directional couplers are measured with pump‐probe experiments, and the origin of the nonlinearity is attributed to fast electronic effects. View full abstract»

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  • Small angle relaxation of highly deformed nematic liquid crystals

    Page(s): 1794 - 1796
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    Transient phase response associated with a small angle relaxation from highly deformed nematic liquid crystal (LC) directors is analyzed experimentally and numerically. Qualitative agreement between computer simulations and experimental results is obtained. Based on these results, decay time of a fast LC modulator employing the transient nematic effect is derived. This decay time is found to be fast (with potential to achieve ∼50 μs), insensitive to LC thickness, but proportional to (λ/Δn0)2, λ being the wavelength and Δn0 the corresponding birefringence. View full abstract»

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  • Optoelectronic transient response of the self‐aligned double‐heterostructure optoelectronic switch

    Page(s): 1797 - 1799
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    Fabrication and characterization of a three‐terminal self‐aligned double‐heterostructure optoelectronic switch in the light‐emitting diode configuration are reported. Results demonstrating device switching characteristics are presented, in which switching is triggered by electrical or optical stimuli. Electrical switch‐on and switch‐off transitions occur in 10 ns, under electrical stimulus. Corresponding optical turn‐on times of 60 ns are observed. With an optical switching energy of 0.02 fJ/μm2, an electrical switch‐on transition of 4 ns is observed. View full abstract»

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  • Electro‐optic phase modulation and optical second‐harmonic generation in corona‐poled polymer films

    Page(s): 1800 - 1802
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    Electro‐optic phase modulation was measured along with optical second‐harmonic generation in thin films of a new copolymer containing a dicyanovinyl‐terminated azo dye side chain. Orientational order was imparted to these films by poling with a corona discharge. Details of the electro‐optic measurement technique, in which the real part of the electro‐optic coefficient can be determined directly, are presented. Taking advantage of the increased orientation imparted by corona poling and the hindered motion of the nonlinear optical moiety in the side chain of the polymer leads to substantial improvements in both the magnitude and stability of nonlinear optical susceptibilities compared to guest‐host polymer systems ordered by electrode poling. View full abstract»

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  • Low‐loss GaAs/AlGaAs waveguide phase modulator using a W‐shaped index profile

    Page(s): 1803 - 1805
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    We demonstrate a low‐loss semiconductor optical waveguide phase modulator for the 1.5 μm wavelength region. The device, based on a p‐i‐n diode/heterostructure waveguide, utilizes a novel epilayer structure to reduce propagation losses associated with doped electrode layers. Propagation loss below 1 dB/cm, significantly lower than previously reported values for conventional semiconductor waveguide phase modulators, was achieved without sacrificing modulator efficiency. View full abstract»

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  • Stopband edges in the dispersion curves of Lamb waves propagating in piezoelectric periodical structures

    Page(s): 1806 - 1808
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    The fractional volume dependence of stopbands in piezoelectric periodical composite plates has been studied experimentally by exciting the band‐edge resonances. The frequency and symmetry of such modes below the thickness resonance of the plate are successfully interpreted in terms of a theoretical model which provides approximate dispersion curves of the lowest Lamb waves propagating in the composite plate. View full abstract»

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  • Pulsed‐ultraviolet laser Raman diagnostics of plasma processing discharges

    Page(s): 1809 - 1811
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    Spontaneous Raman spectroscopy with pulsed‐ultraviolet laser excitation of the Stokes vibrational Raman lines was used to measure the percent dissociation of nitrogen and sulfur hexafluoride in low‐pressure radio refrequency discharges of the type used for processing semiconductor materials. Measurements of the percent dissociation of sulfur hexafluoride, at pressures between 200 and 600 mTorr, show a strong pressure dependence which is consistent with recombination playing an important role in sulfur hexafluoride discharge kinetics. View full abstract»

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  • Reinvestigation of the carbon films prepared by ArF excimer laser‐induced chemical vapor deposition

    Page(s): 1812 - 1814
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    It has already been reported by the authors [K. Kitahama, K. Hirata, H. Nakamatsu, S. Kawai, N. Fujimori, T. Imai, H. Yoshino, and A. Doi, Appl. Phys. Lett. 49, 634 (1986)] that the formation of diamond was confirmed in an ArF excimer laser‐induced chemical vapor deposition experiment using acetylene as a carbon source. However, a careful reexamination of the reflection electron diffraction photographs afterward reveals that the deposit is something other than diamond. Raman spectra of the deposit were compared with those of other homologous substances. It is concluded that the structure of the deposit consists of individual graphite layers which are randomly translated parallel to the layers and rotated about the normal of the layers, although separations between individual graphite layers are kept constant. The structure is identical with that of the material known as a ‘‘heat‐treated carbon black.’’ View full abstract»

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  • Selective deposition of diamond crystals by chemical vapor deposition using a tungsten‐filament method

    Page(s): 1815 - 1817
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    Selective deposition of polycrystalline and single‐crystal diamonds has been achieved on a silicon wafer by chemical vapor deposition from CH4 and H2 gases using a hot‐filament method. The nucleation of diamonds occurs selectively at the sites fabricated by successive roughening and patterned etching of wafers. View full abstract»

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  • Characterizations of the dc discharge plasma during chemical vapor deposition for diamond growth

    Page(s): 1818 - 1819
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    During the course of diamond growth by dc plasma chemical vapor deposition, characteristics of the plasma have been measured by means of the Langmuir single probe method and emission spectrometry. For the source gas system of hydrogen and methane (gas ratio: CH4/H2=2/100, total gas pressure: 2.66×104 Pa), it is revealed that the statistical temperatures of hydrogen atoms and electrons in the positive column of the plasma are obtained to be 4.8×103–5.3×103 K and 1×105–1.1×105 K, respectively. The amount of ionized species is fairly small. By calculating the equilibrium constant of gas molecules in these gas temperature ranges, it is found that molecules over 99% H2 and CH4 are decomposed to the neutral H and C atoms. View full abstract»

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  • Hydrogen‐induced crystal to glass transformation in Zr3Al

    Page(s): 1820 - 1822
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    The process of hydrogen‐induced amorphization of the equilibrium intermetallic compound Zr3Al is compared to ion‐irradiation‐induced amorphization of the same compound. In contrast to ion irradiation, where almost complete chemical disordering precedes the onset of amorphization, hydrogenation of Zr3Al causes no appreciable change in long‐range order prior to amorphization. Electron microscopy reveals apparent homogeneous nucleation of the amorphous phase, and striking similarities to martensitic microstructures. The maximum lattice dilation observed prior to amorphization by hydrogen absorption is identical to that found during irradiation, indicating that lattice expansion is a common measure of the crystal instability induced by different solid‐state processing techniques. View full abstract»

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  • On epitaxial growth of diamond films on (100) silicon substrates

    Page(s): 1823 - 1825
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    We have investigated characteristics of polycrystalline diamond thin films formed by plasma‐enhanced chemical vapor deposition method on silicon substrates using Raman spectroscopy, analytical and high‐resolution transmission electron microscopy techniques. Grains with average size 1 μm in diameter were observed in these films. The Raman spectra from these films contain the strongest peak at 1335 cm-1, providing the characteristic signature for sp3 (diamond) bonding. The broad peak centered around 1550 cm-1 is believed to be due to some graphitic bonding. From detailed high‐resolution images and microdiffraction, films were characterized to be cubic diamond with a lattice parameter of 3.56 Å. Diamond crystallites with fivefold external morphologies were also observed. The large crystallites in the films exhibited preferential texture in 〈011〉 type orientations. These crystallites were found to be twinned in {111} planes. The large 〈011〉 crystallites exhibited matching in {111} or {200} lattice planes of diamond with {022} planes of silicon. This is in agreement with our previous work on the growth of Ni on MgO, which showed that textured growth can occur by matching a set of lattice planes in the absence of matching of lattice constants. View full abstract»

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  • Short‐wavelength (≲6400 Å) room‐temperature continuous operation of p‐n In0.5(AlxGa1-x)0.5P quantum well lasers

    Page(s): 1826 - 1828
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    Data are presented demonstrating short‐wavelength (≲6400 Å) continuous (cw) laser operation of p‐n diode In0.5(AlxGa1-x)0.5P multiple quantum well heterostructure (QWH) lasers grown lattice matched on GaAs substrates using metalorganic chemical vapor deposition. In the range from -30 °C to room temperature (RT≊300 K, λ≊6395 Å) the threshold current density changes from 2.3×103 A/cm2 (-30 °C) to 3.7×103 A/cm2 (RT, 300 K). The cw 300 K photopumped laser operation of the same quaternary QWH crystal is an order of magnitude lower in threshold (7×103 W/cm2, Jeq∼2.9×103 A/cm2) than previously reported for this crystal system, and agrees with the successful demonstration of cw 300 K laser diodes at this short wavelength. View full abstract»

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  • Thermally and light‐induced instabilities in phosphorus‐doped hydrogenated amorphous silicon

    Page(s): 1829 - 1831
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    Changes in the gap‐state profile of phosphorus‐doped hydrogenated amorphous silicon films subjected to light soaking and thermal quenching have been studied by isothermal capacitance transient spectroscopy. No suggestive changes due to thermal quenching are observed in the density‐of‐states distribution at least in the energy range 0.25–1.50 eV below the conduction‐band edge (Ec). On the other hand, gap states are created in the range of 0.25–0.35 eV below Ec by light soaking, in addition to the conversion from deeper states located 1.0–1.2 below Ec to shallower states located 0.4–0.6 below Ec. These results suggest that the effects of light soaking and thermal quenching are apparently independent of each other. View full abstract»

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  • Infrared characterization of UV laser‐induced silicon oxide films

    Page(s): 1832 - 1834
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    Oxygen incorporation and subsequent oxidation of ion‐implanted silicon have been performed using repetitive pulsed excimer laser irradiation working in the liquid phase regime. The kinetics of the oxidation and the characterization of the grown SiO2 were investigated by infrared spectroscopy. The origin of the broadening of the Si‐O stretching band of these oxides grown from the liquid phase is discussed. View full abstract»

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  • Growth and characterization of Ge/Si strained‐layer superlattices

    Page(s): 1835 - 1837
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    Ultrathin Ge/Si strained‐layer superlattices (SLS’s) with periodicities of a few monolayers have been successfully grown and characterized by Raman scattering spectroscopy. Structures with alternating Ge and Si layers were grown on Si substrates of different orientations. A thick 200 nm Ge0.4Si0.6 buffer layer was grown prior to the growth of the superlattice to make the strain distribution of the superlattice symmetrical and thus to maintain the pseudomorphic growth of the superlattices. Folded acoustic phonon peaks observed from these Ge/Si SLS samples can be used to determine the superlattice periodicity. The observed optical phonon frequencies were found to depend strongly on superlattice periodicity. A quantitative interpretation of this phenomenon was presented. Subsequent annealing of these samples reveals that the transition from pure Ge and/or Si layers to GexSi1-x alloy becomes more pronounced as the annealing time and temperature increase. View full abstract»

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  • Ion beam induced oxidation of silicon

    Page(s): 1838 - 1840
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    A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon is controlled by the impact of an energetic ion beam on a clean silicon target exposed to low‐pressure oxygen. An oxide layer of 50–100 Å can be formed at room temperature by properly choosing the oxidation conditions. The growth was studied in situ by measuring the ion‐induced secondary electron yield. A strong dependence on oxygen pressure and target temperature was observed. By studying the oxide with x‐ray photoelectron spectroscopy, it was concluded that the film formed is stoichiometric SiO2 . A discussion on possible growth mechanisms is carried out in terms of ion energy deposition. View full abstract»

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  • Physical meaning of electron capture kinetics on DX centers

    Page(s): 1841 - 1843
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    The capture kinetics of electrons on DX centers are interpreted in terms of a simple model taking only into account the fact that the concentrations of the DX centers and of the doping impurities are equal. It is shown that there is no need to introduce an alloying effect in order to explain the capture as well as the emission kinetics, in agreement with the nonobservation of this effect in optical transitions. This is understood if the DX center is itself the donor impurity. View full abstract»

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  • Time‐resolved reflectivity techniques for dynamic studies of electron beam recrystallization of silicon‐on‐insulator films

    Page(s): 1844 - 1846
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    A time‐resolved reflectivity (TRR) technique has been developed for dynamic studies of swept beam heating of silicon‐on‐insulator (SOI) materials. The method exploits the temperature dependence of the reflectivity of SOI films to allow noncontact temperature measurement with high spatial and temporal resolution. This technique is of considerable practical importance for beam processing, since it allows the temperature distribution induced by a beam being scanned across a specimen to be determined. The temperature distribution produced by a line electron beam swept across a SOI specimen was experimentally measured and found to be consistent with a theoretical prediction. The TRR technique can also be used to study melting and will prove useful for characterizing zone melting recrystallization, where thermal modeling is often inadequate for the complex structures involved. View full abstract»

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  • Growth of CdTe‐InSb multilayer structures on (100) InSb substrates using molecular beam epitaxy

    Page(s): 1847 - 1849
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    Molecular beam epitaxy has been used to grow multilayer structures of CdTe/InSb on (100)InSb substrates. To minimize interdiffusion effects, a particularly low growth temperature was used. This study presents the first transmission electron microscope and secondary‐ion mass spectrometer investigations of this multilayer system. The work clearly demonstrates that the multilayers have high structural quality and that there is no large scale interdiffusion of the matrix elements. Roughening is observed at the ‘‘InSb grown on CdTe’’ interface, although only relatively minor undulations are present at the inverted interface. A possible explanation for this effect is described. View full abstract»

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  • Minority‐carrier lifetime of magnetic field applied Czochralski silicon wafers

    Page(s): 1850 - 1852
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    The dependence of minority‐carrier lifetimes and diffusion length on starting silicon materials grown by the magnetic field applied Czochralski (MCZ), conventional Czochralski(CZ), and float‐zone (FZ) methods has been investigated with a capacitance‐time relaxation technique. MCZ silicon yields longer minority‐carrier lifetimes and diffusion length than those of both CZ and FZ silicon materials. The generation lifetime of MCZ silicon increases, while the recombination lifetime decreases, with the initial oxygen concentration. These characteristics are correlated with grown‐in defects and gettering by oxygen‐related defects. View full abstract»

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

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Nghi Q. Lam
Argonne National Laboratory