bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron beam generation by electron multiplication
Authors: Murray C. , Szapiro B. , Rocca J. J.
Published: July 2002

We have demonstrated that intense pulsed electron beams can be created by multiplication of lower current electron streams impinging on a high electron yield target. A 17 A electron beam of 1 μs pulse width was generated from a 2.5 A beam bombarding an activated Ag-Mg target 2.5 cm in diameter.
Coherent Zener tunneling in InAs electron inversion layers
Authors: Kunze U.
Published: July 2002

In an electron inversion layer on a degenerate p-type InAs substrate, a resonance effect is observed in tunneling from the two-dimensional electron gas into the continuum of valence states. The effect is confirmed by additional magnetotunneling measurements.
InP/InGaAsP buried mesa ridge laser: A new ridge laser with reduced leakage currents
Authors: Jung H. , Schlosser E.
Published: July 2002

We describe a new kind of InP/InGaAsP buried ridge laser—the buried mesa ridge laser. A simple calculation shows that this laser structure has considerably reduced leakage currents compared with the conventional buried ridge laser. The fabrication steps are described. The light-current characteristic curve measured on the InP/InGaAsP buried mesa ridge laser shows a linear behavior up to 40 mW, the highest value reported so far for the buried ridge type laser.
Determination of effective optical constants of magnetic multilayers
Authors: Deeter M. N. , Sarid D. , England C. D. , Bennett W. R. , Falco Charles M.
Published: July 2002

The effective optical and magneto-optical constants of a series of Cu/Co multilayer films are determined experimentally and compared with a theoretical thin-film model based on the bulk optical constants of Cu and Co. In the multilayer series, the atomic percentages of Cu and Co were kept fixed and the period varied from 0.4 to 13.6 nm. Deviations from bulk-like behavior in the effective optical constants are observed for multilayers with periods less than 3 nm.
Picosecond pulse amplification by wave mixing in GaAs
Authors: Ma H. M. , Li F. M.
Published: July 2002

Pulses at 1.064 μm were amplified up to 102 times by nonlinear mixing with a coherent pump wave in GaAs. The observed amplification shows a strong dependence on the intersection angle and time delay between pump and probe pulses. The effect is discussed in terms of self-diffraction by a laser-induced free-carrier grating.
Fidelity of optical phase conjugation by degenerate four-wave mixing in semiconductor glasses and ruby
Authors: Saltiel S. M. , Van Wonterghem B. , Parthenopoulos D. A. , Dutton T. E. , Rentzepis P. M.
Published: July 2002

The fidelity of phase conjugation by degenerate four-wave mixing in ruby and semiconductor-doped glasses has been measured by means of our own modified Twyman–Green interferometer [Opt. Lett. 14, 183 (1989)] implementing two phase conjugate mirrors. It is shown that the fidelity of phase conjugators with an OG530 color filter as the nonlinear medium reaches a value of 99%. The fidelity of ruby is also reported. Additionally the effect of the recording system on the value of the fidelity is discussed.
Observation of positive and negative nonlinear gain in an optical injection experiment: Proof of the cavity standing-wave-induced nonlinear gain theory in 1.3 μm wavelength semiconductor diode lasers
Authors: Eom J. , Su C. B.
Published: July 2002

The origin of nonlinear gain in 1.3 μm InGaAsP semiconductor diode lasers is studied by measuring the magnitude and phase of a probe laser’s frequency response to optical injection with orthogonally polarized light from a pump laser. The sign and magnitude of the gain nonlinearity induced by optical injection depend on wavelength separation between pump and probe laser. The maximum magnitude of the nonlinear gain parameter is about 1.5×10−15 cm2. These results are consistent with the recently proposed theory that nonlinear gain is caused by the feedback from the dielectric grating induced by the standing wave in the laser cavity.
X-ray photoemission studies of the interfacial reactions of Pt and Au on anodic oxide of Hg0.8Cd0.2Te
Authors: Lau W. M. , He J.-W. , Norton P. R.
Published: July 2002

The metal-oxide interfacial reactions of platinum and gold on anodic oxide of Hg0.8 Cd0.2 Te have been studied by x-ray photoelectron spectroscopy. It was found that the depositions of these metals, which were expected to be inert, reduced the oxidized tellurium in the anodic oxide and extracted the reduced tellurium into the metal overlayer. In the case of platinum, reductions of oxidized cadmium and mercury also occurred. The resultant interfacial structures of gold and platinum on HgCdTe oxide seem to be determined by the kinetics of possible reactions but not by bulk thermodynamic data of the relevant reactants and the most stable reaction products.
Study on the stabilization of the high T
c phase in a BiSrCaCuO system
Authors: Lee H. G. , Kim C. J. , Lee K. H. , Won D. Y.
Published: July 2002

A high Tc superconductor of Pb-doped BiSrCaCuO with a Tc of 102 K was prepared. A new phase distinguished from that of undoped BiSrCaCuO was formed by Pb doping. It is reported that the Pb doping, sintering time, and low-temperature anneal are important to stabilize the high Tc phase in BiSrCaCuO. The Jc value (77 K, H=0) was measured as 23 A/cm2.
Superlattice modulation and epitaxy of Tl2Ba2Ca2Cu3O10 thin films grown on MgO and SrTiO3 substrates
Authors: Chen C. H. , Hong M. , Werder D. J. , Kwo J. , Liou S. H. , Bacon D. D.
Published: July 2002

We compare the superlattice modulation, microstructure, and epitaxy of Tl2Ba2Ca2Cu3O10 thin films grown on MgO [100] and SrTiO3 [100] substrates by dc diode sputtering. Films grown on MgO were found to be quite clean with the c axis perpendicular to the substrate. However, no in-plane orientational relationship to the substrate was found. Films grown on SrTiO3, on the other hand, showed very good epitaxy to the substrate despite the presence of second phases. Films grown on MgO also exhibited a longer coherence length of the superlattice modulation than those grown on SrTiO3 under identical conditions.
Interfacial charge modification between SiO2 and silicon
Authors: Aronowitz S. , Zappe H. P. , Hu C.
Published: July 2002

A positive flatband voltage shift, ΔVfb ≂+0.4 V, with respect to unimplanted portions of the same wafer, was obtained when calcium (1×1013 cm−2) was implanted into 87 nm of thermally grown oxide on an n-type 〈100〉 substrate and annealed. Calcium acts as a low-efficiency n-type dopant in silicon (<0.1% activated) which eliminates the possibility of calcium interactions in the substrate causing the flatband behavior. Calcium profiles after a 1100 °C anneal show considerable loss from the oxide but also indicate occurrence of stable sites in the SiO2 region near the oxide-silicon interface. Theoretical calculations on a model SiO2 structure predict an effective negative charge at the Si/SiO2 interface due to calcium incorporation in agreement with the general behavior observed experimentally; moreover, the calculations predict that aluminum and strontium will behave in a similar fashion to calcium when implanted into SiO2 while boron will not.
Evidence for the superconducting proximity effect in junctions between the surfaces of YBa2Cu3Ox thin films
Authors: Moreland John , Ono R. H. , Beall J. A. , Madden M. , Nelson A. J.
Published: July 2002

We have used the squeezable electron tunneling junction technique for testing the electrical properties of the surfaces of YBa2Cu3Ox (YBCO) thin-film electrodes. As deposited and annealed, the surfaces of the electrodes were insulating at 4 K. Several methods were used to improve the electrical properties of the electrodes’ surfaces including rapid thermal annealing, oxygen sputter etching, and thin Ag coating treatments. The greatest improvement occurred after a deposition of a 5 nm Ag coating and subsequent rapid thermal anneal of one set of YBCO films. Under these conditions it was possible to make a superconducting Josephson point contact between the surfaces of the electrodes. We think that the Ag acts as a normal-metal proximity layer effectively shunting the degraded electrodes’ surfaces.
Novel features of rapidly quenched melts of Bi2(Ca,Sr)3Cu2O8+δ
Authors: Varma K. B. R. , Rao K. J. , Rao C. N. R.
Published: July 2002

By roller quenching and water quenching melts of Bi2(Ca, Sr)3Cu2O8+δ, glasses have been obtained. These glasses exhibit two glass transitions as well as two crystallization transitions. Microwave absorption studies show the glass to be weakly superconducting at 77 K, probably due to the presence of ultramicrocrystallites. The glass on crystallization at 870 K gives the crystalline n=1 member of the homologous series Bi2(Ca, Sr)n+1CunO2n+4 and the n=2 member on annealing at 1100 K. The glass route provides a unique means of obtaining the n=2 member of the series. On prolonged annealing of the glass at 1120 K, the n=3 member seems to be formed.
Increased T
c of bismuth strontium calcium copper oxide superconductor by praseodymium substitution
Authors: Geller S. , Wu K.-Y.
Published: July 2002

It is shown that a small substitution of praseodymium for bismuth as in Pr0.05Bi1.95Sr2CaCu2.2O8.2+δ produces a significant increase, 13 K, in the onset temperature, 7 K in the temperature at which the whole specimen is superconducting, and 10 K in the transition-midpoint temperature relative to Bi2Sr2CaCu2.2O8.2+δ. Unfortunately the transition is broadened, 20 K versus 14 K. Doubling the amount of praseodymium substitution causes the occurrence of extraneous phase(s), the effect of which is seen only in the resistance versus temperature data, and does not indicate any additional significant increases in the aforementioned temperatures.
Self-pumped phase conjugation in potassium niobate (KNbO3)
Authors: Rytz D. , De Zhong Shen
Published: July 2002

Self-pumped phase conjugation is observed using a KNbO3 crystal. The reflectivity of an external ring phase conjugate mirror is measured as a function of temperature for 515 nm radiation. The maximum reflectivity is 26% at 124 °C. On cooling, the reflectivity decreases and vanishes completely below 62 °C. The phase conjugate nature of the retroreflected beam is illustrated. The temperature-dependent response time is shown to be proportional to (T−56 °C)−1.
Intermetallic structure of laser reflowed Cu/Pb-Sn solder joints
Authors: Felton L. E. , Selsley A. D. , Ficalora P. J.
Published: July 2002

A Nd:YAG laser was used to reflow Cu/Pb-Sn solder joints. The joints were reflowed with 60 W, 1 s laser pulse. The resulting intermetallic microstructure was examined with scanning electron microscopy, energy dispersive x-ray analysis, and x-ray diffraction. In addition to the intermetallic layer expected to form at the solder-base metal interface, an intermetallic precipitate was found to form in the bulk solder. X-ray diffraction data established the identity of the intermetallic as η-Cu6Sn5.
200 MW S-band Dielectric Cherenkov Maser oscillator
Authors: Main William , Cherry Randall , Garate Eusebio
Published: July 2002

General Dynamics is investigating the Dielectric Cherenkov Maser as a rugged, compact, and tunable high-power microwave source. This letter reports the test results of an S-band device operating at 3.8 GHz. The device consisted of a dielectric (ε=10) lined cylindrical waveguide with waveguide radius 3.63 cm, and liner thickness 0.60 cm; and an annular electron beam with radius 2.54 cm. The beam parameters were 700 keV, 12 kA, 100 ns and yielded an rf pulse of 200 MW for 20 ns. A 15 kG axial guide field was used. The measured results agree with the numerical solution of the dispersion relation which includes the effect of the beam and liner.
Comparison of interplanar-boson-exchange models of high-temperature superconductivity—possible experimental tests
Authors: Casella R. C.
Published: July 2002

Semiquantitative tests are considered of models, proposed earlier by this author, in which high Tc superconductivity follows from the exchange of unspecified intermediate bosons (IB) with ω≫ωphonon between fermionic pairs in different CuO2 layers. Earlier predictions of the dependence of Tc(n) on the number n of layers per cluster are extended to include the possibility that Tc(n=1)<∼10 K in the Tl 1201 and 2201 compounds. In common with other authors rapid saturation of Tc(n) with increasing n is found here. Nonetheless, the experimental value of Tc(n=1) in the Tl and Bi systems can play an important role in discriminating between the various models empirically.
Continuous growth of heavily doped p+-n+ Si epitaxial layer using low-temperature photoepitaxy
Authors: Yamazaki Tatsuya , Minakata Hiroshi , Ito Takashi
Published: July 2002

Heavily doped p+ and n+ silicon epitaxial layers were continuously grown at 600 °C using photoenhanced epitaxy. The heavily phosphorus-doped photoepitaxial layer with a carrier concentration above 1×1017 cm−3 grown on the p− substrate shows very high density surface pits due to phosphorus precipitation, suggesting poor crystal quality. Unexpectedly, when this n+ photoepitaxial layer is continuously grown on a heavily boron-doped p+ photoepitaxial layer at a boron concentration above 1×1019 cm−3, surface pits completely disappear and crystal quality is greatly improved. The very low growth temperature enabled an extremely abrupt impurity profile to be achieved for the p+-n+ layer.
Measurement of multigigahertz waveforms and propagation delays in modulation-doped field-effect transistors using phase-space absorption quenching
Authors: Wiesenfeld J. M. , Heutmaker M. S. , Bar-Joseph I. , Chemla D. S. , Kuo J. M. , Chang T. Y. , Burrus C. A. , Perino J. S.
Published: July 2002

High-speed waveforms (up to 20 GHz) in InGaAs/InAlAs modulation-doped field-effect transistors (FETs) are measured using 10–20 ps optical probe pulses via the quenching of the absorption in the quantum well gate channel due to Pauli exclusion. The technique is a noncontact probe of the charge density in the gate, and hence, of the logic state of the FET. This charge-sensitive probing technique is combined with voltage-sensitive electro-optic sampling to study internal dynamics of the FET. A gate channel charging time of 11 ps and a gate to drain propagation delay of 15 ps are measured.
Asymmetric dual quantum well laser—wavelength switching controlled by injection current
Authors: Ikeda Sotomitsu , Shimizu Akira , Hara Toshitami
Published: July 2002

We have performed the first experiment on a novel laser diode, the lasing wavelength of which can be switched with increasing current. Wavelength switching over 13 nm under continuous operation, as well as lasing at dual wavelengths, has been achieved for the first time.
Dielectric liquids for possible use in pulsed power switches
Authors: Christophorou L. G. , Faidas H.
Published: July 2002

Dielectric liquids for possible use as (opening/closing) switching materials in pulsed power technology are identified. A concept for a dielectric-liquid-pulsed-power switch employing flashlamps is outlined.
Characterization of the CoGa/GaAs interface
Authors: Zhu Jane G. , Carter C. Barry , Palmstro/m C. J. , Garrison K. C.
Published: July 2002

The interface between the (001) surface of GaAs and a CoGa layer grown by molecular beam epitaxy has been characterized using transmission electron microscopy in plan view and cross-sectional view. The interface is found to consist primarily of a network of edge dislocations with Burgers vectors a[100] and a[010] (a being the lattice parameter of the CoGa). The occurrence of these Burgers vectors indicates that these misfit dislocations are nucleated in the CoGa during growth. It is clearly shown that the threading dislocations in the CoGa originate at the misfit dislocations at the interface, while the GaAs layer underneath is free of dislocation.
Well size related limitations on maximum electroabsorption in GaAs/AlGaAs multiple quantum well structures
Authors: Jelley K. W. , Engelmann R. W. H. , Alavi K. , Lee H.
Published: July 2002

Experimentally determined maximum electroabsorption in GaAs/Al0.33Ga0.67As multiple quantum wells over the quantum well width range of 17–260 Å is related to the confinement of the electronic wave functions in the quantum well, increasing with enhanced confinement. However, for very narrow wells, this increase in maximum electroabsorption is diminished by strong broadening of the excitonic resonances due to phonon scattering, eventually leading to a peak value of 22 200 cm−1 at a 35 Å well width.
Direct observation of atomic planes in epitaxial multilayers by anodization spectroscopy
Authors: Blamire M. G. , Huang K. H. , Somekh R. E. , Kirk E. C. G. , Morris G. W. , Evetts J. E.
Published: July 2002

Using the technique of anodization spectroscopy we have shown that it is possible to directly observe individual atomic planes in high quality Nb/Ta epitaxial multilayers. The signal corresponding to the atomic planes is superimposed on the superlattice structure associated with the different anodization rates of the two metals. The results imply that an upper limit of less than 0.1 nm can be placed on the fundamental resolution of this novel measurement technique. As a test of this measurement we have obtained data from films grown on different orientation substrates, and have shown that the separation of the peaks corresponds to the known lattice spacings in the growth direction. The mechanisms responsible for the very uniform propagation of the anodization front and the consequent ability to observe directly the atomic planes normal to the exposed surface are discussed.
Disordering of ZnSe/ZnS strained-layer superlattices by Si ion implantation
Authors: Saitoh Tohru , Yokogawa Toshiya , Narusawa Tadashi
Published: July 2002

Disordering of ZnSe/ZnS strained-layer superlattices(SLSs) induced by Si ion implantation and subsequent low-temperature thermal annealing was confirmed. Si ions were implanted (100 keV, 1×1016 ions/cm2 ) into SLSs (140 Å ZnSe-140 Å ZnS, ten periods). By secondary-ion mass spectrometry analyses, periodic profiles of Se and S were clearly observed just after the ion implantation; however, they disappeared after subsequent thermal annealing (450 °C, 3 h). Photoluminescence measurements showed the peak of ZnSx Se1−x alloyed crystal after thermal annealing. The disordering is mainly induced by the diffusion of defects generated by the ion implantation at the early stage of low-temperature thermal annealing. This low temperature and planar process will be very useful to the fabrication of II-VI compound semiconductor optical and electrical devices.
Cyclotron resonance of two-dimensional holes in strained-layer quantum well structure of (100)In0.20Ga0.80As/GaAs
Authors: Lin S. Y. , Liu C. T. , Tsui D. C. , Jones E. D. , Dawson L. R.
Published: July 2002

Cyclotron resonance of the two-dimensional hole gas (2DHG) in the strained-layer quantum well structure of In0.20Ga0.80As/GaAs is observed in far-infrared transmission measurements made at 4.2 K. The cyclotron mass of the 2DHG in the In0.20Ga0.80As channel is (0.191±0.008)me for a 2D hole density p2D =8.5×1011/cm2.
Integration of a Faraday rotator and a mode selector for a magnetic field sensor
Authors: Matsuda Kaoru , Ishizuka Satoshi
Published: July 2002

We have demonstrated an integrated magnetic field sensor consisting of a Faraday rotator and a mode selector for the first time. The sensor is a loaded waveguide which has a waveguide layer made of a garnet with magneto-optical effect for Faraday rotation and a metal clad layer for mode selection. The magnetic field can be measured by detecting the change of optical output power from the waveguide. An output power change of ±5% has been observed as the magnetic field is changed from zero to ±60 Oe.
Room-temperature absorption study of CdTe-ZnTe superlattices
Authors: Shtrikman Hadas , Riezman A. , Tenne R. , Mahalu D. , Finkman E.
Published: July 2002

Room-temperature photoconductivity measurements were carried out on metalorganic chemical vapor deposition grown CdTe-ZnTe superlattices with a periodicity of 30–80 Å. The threshold of the photoconductivity measurements varied with the size of the well. Transition of the electron to the n=1 level in the conduction band was observed in all samples; the transition to the n=2 level was found for the superlattices with well width exceeding 25 Å. These findings agree very well with room-temperature absorption measurements performed on the same superlattices and with model calculations which were based on the Kronig–Penney model with Bastard’s boundary conditions.
130 GHz GaAs monolithic integrated circuit sampling head
Authors: Marsland R. A. , Valdivia V. , Madden C. J. , Rodwell M. J. W. , Bloom D. M.
Published: July 2002

We have fabricated a GaAs diode sampling head which has a bandwidth of 130 GHz, which is a five times improvement over previous room-temperature designs. This speed is attained with a monolithic sampling head design integrated with two nonlinear transmission lines which serve as the strobe pulse and test signal generators. A 4 ps transition time has been measured with the sampler. We have also measured sinusoidal waveforms to 120 GHz.
Spectroscopic evidence of two-dimensional character of the 90 K Bi2(Sr,La,Ca)3Cu2O8 superconductors
Authors: Lindberg P. A. P. , Shen Z.-X. , Wells B. O. , Dessau D. S. , Borg A. , Lindau I. , Spicer W. E. , Mitzi D. B. , Kapitulnik A.
Published: July 2002

Polarization-dependent angle-resolved photoemission experiments in the constant final state mode (absorption measurements) were performed on single crystals of the Bi-based 2212 material using synchrotron radiation in the photon energy range 10–40 eV. Evidence of polarization-dependent transitions due to Bi 5d→6p, Sr 4p→4d, and Ca 3p→3d excitations is observed. The data show that the electronic charge is highly localized to the layers of the crystal structure, thus providing a direct spectroscopic confirmation of the two-dimensional nature of these types of materials. Polarization-sensitive absorption signals at 14–15 eV attributed to Bi 6s→6p transitions show that the density of states (DOS) of the Bi 6pz holes peaks at about 0.7 eV higher energy than the DOS of the Bi 6px,y holes.
I
n s
i
t
u measurement of micromass of the fuel in a cryogenic foam target for laser fusion research
Authors: Katayama H. , Norimatsu T. , Kato Y. , Yamanaka T. , Nakai S.
Published: July 2002

We have presented a novel in situ method which is simple and sensitive, to measure the micromass of the fuel layer in a cryogenic foam target. In this method, a foam shell is mounted on a flexible polyester fiber 7 μm in diameter and 800 μm in length. The fiber is suspended with a stalk which is mechanically vibrated at any given frequency. The resonant frequency of the elastic vibration of a foam-fiber system is measured before and after fuel loading. The mass of the fuel can be determined from the change in the resonance frequency in the range from submicrograms to submilligrams. The resolution of this system, which is limited by the Q factor of the foam-fiber system, is better than 0.2 μg corresponding to the measurement accuracy of 0.1%.
Growth of InGaAs in a hot-walled vapor phase epitaxy reactor using a trimethylarsenic source
Authors: Buckley D. N.
Published: July 2002

Trimethylarsenic was used as a group V source in a hot-walled vapor phase epitaxy (VPE) reactor. High quality InGaAs was grown. Samples with no intentional doping were n type with a background carrier concentration of 6×1015 cm−3, about three times higher than that of comparison samples grown using arsine. Mobilities measured at 77 and 300 K, respectively, were similar to those measured for corresponding samples grown using arsine, suggesting that, in contrast with metalorganic chemical vapor deposition using trimethylarsenic, no significant carbon incorporation occurred. It is concluded that the prognosis is good for the replacement of arsine in hot-walled VPE reactors by an arsenic alkyl such as trimethylarsenic.
Characterization of cladded glass fibers using acoustic microscopy
Authors: Jen C. K. , Neron C. , Bussiere J. F. , Li L. , Lowe R. , Kushibiki J.
Published: July 2002

Spatial distribution profiles of leaky surface acoustic wave velocity (VLSAW ) and attenuation across the diameters of cladded glass fibers are presented. The profiles are obtained by using a novel V(x,z) analysis with a reflection scanning acoustic microscope operated at 775 MHz, and are compared with optical refractive index profiles. Optical fibers with different dopants and dopant concentrations have been investigated. The role of acoustic property profiles in the design of optical and acoustic fibers is outlined.
Picosecond single-mode pulse compression using a 1.3 μm Fabry–Perot laser diode, a dispersion-shifted fiber, and a grating monochromator
Authors: Takahashi Ryo , Liu Hai-Feng , Osiński Marek , Kamiya Takeshi
Published: July 2002

A single longitudinal mode optical pulse train with a full width at half maximum less than 7.2 ps was generated by compressing gain-switched pulses from a 1.3 μm multimode laser diode using a monochromator and a dispersion-shifted single-mode optical fiber.
Novel technique for Si epitaxial lateral overgrowth: Tunnel epitaxy
Authors: Ogura Atsushi , Fujimoto Yuki
Published: July 2002

A novel technique for Si epitaxial lateral overgrowth, called tunnel epitaxy, is proposed and demonstrated. In this technique, lateral epitaxy proceeds in the tunnel between the upper and lower SiO2 layers. Limitation of film thickness is achieved, as is a high lateral/vertical growth ratio of approximately 7. Lateral growth distance is limited by clogging of the gas injection window by polycrystalline Si grain growth. Rough surface morphology and twin boundary defects were observed in the fabricated silicon-on-insulator. The origins of and possible solutions for these problems are discussed.
Electrical characteristics of regrown interfaces using diethylgallium chloride-based metalorganic vapor phase epitaxy
Authors: Tischler M. A. , Kuech T. F. , Palevski A. , Solomon P.
Published: July 2002

The electrical characteristics of regrown interfaces deposited using an alternate metalorganic chemistry, diethylgallium chloride (DEGaCl), are investigated. With the appropriate HCl pre-regrowth surface treatment, these interfaces are found to be of very high quality with no substantial interface charge. The contact resistivity, as determined by transmission line measurements, is (2–4)×10−7 Ω cm2 at both 77 and 300 K. Secondary-ion mass spectroscopy measurements show no detectable accumulation of impurities at the regrown interface, in contrast to those regrown using the conventional trimethylgallium-based chemistry.
Thermal characteristics of a split-disk geometry glass laser amplifier
Authors: Kim Byung-Tai , Nakatsuka Masahiro , Kanabe Tadashi , Nakai Sadao
Published: July 2002

Thermal characteristics of a split-disk amplifier system with 50 mm diam aperture were measured by a Schlieren method with a ball stopper of 88 μm diam under repetitively pulsed operation for a pump loading of up to 1 kW(1 kJ/ Hz). The thermal beam divergence reached 100 μrad at an average input power of 200 W(1 kJ/0.2 Hz) under 300 ℓ/min(0.73 m/s) N2 gas flow. The thermal limitations of this amplifier system are discussed under repetitive operation.
Lateral interface mixing in GaAs quantum well wire arrays
Authors: Fukui Takashi , Saito Hisao , Tokura Yasuhiro
Published: July 2002

GaAs quantum well wires with an (AlGaAs)1/2(GaAs)1/2 fractional-layer superlattice(FLS) are fabricated on slightly misoriented (001)GaAs substrates by metalorganic chemical vapor deposition. Transmission electron microscope images show clear contrast for the GaAs quantum wire array, although the lateral heterojunction interface is a little diffusive. Photoluminescences are measured for a quantum well wire array having both FLS and GaAs layers as the well region. From a comparison of measured and calculated photoluminescence energies, the thickness of the lateral interface mixing layer is estimated to be 1–2 nm.
Heteroepitaxial growth of ZnSe on (100) Si by low-pressure organometallic chemical vapor deposition
Authors: Lee M. K. , Yeh M. Y. , Chang C. C.
Published: July 2002

ZnSe epitaxial layers were successfully grown on (100) Si substrates by low-pressure organometallic chemical vapor deposition. The initial growth rate is not critical. The optimum growth temperature of ZnSe/Si is higher than that of ZnSe/GaAs. From x-ray and scanning electron microscopy examinations, single crystalline ZnSe epilayers with mirror-like surfaces can be obtained by a simple growth process. Two-step growth process is a suitable way to improve the ZnSe/Si quality. It seems to be able to remove the Zn vacancy which is associated with the photoluminescence broad band. The efficient 77 K photoluminescence indicates that the ZnSe epilayers are of good quality.
Effect of heat treatments on the electrical resistivity of Sb-doped amorphous Si films deposited by molecular beam on (100) Si
Authors: Komem Y. , Arienzo M. , Iyer S. S.
Published: July 2002

Amorphous silicon films, doped with antimony at a relative high concentration of ∼(4–5)×1020 cm−3, were deposited by means of a molecular beam on (100) Si substrates. These films were subsequently heat treated at temperatures between 500 and 700 °C for times between 5 s and 12 h. It was found that at 500 °C the resistivity decreased with time during solid phase epitaxial growth of the amorphous films and induced electrical activation of Sb ‘‘quenched-in’’ the Si. At the higher temperatures, however, after an initial decrease to a minimum value the resistivity increased with the heat treatment time as a result of a precipitation of Sb from the supersaturated crystallized Si films. The times to obtain the minimum values of the resistivity are consistent with the rates of the solid phase epitaxial growth of amorphous Si films on (100) Si given in the literature for the various temperatures.
AlxGa1−xN polarity determination by x-ray diffraction
Authors: Horning R. D. , Goldenberg B. L.
Published: July 2002

The crystallographic polarities of (0001) oriented AlxGa1−xN epitaxial layers grown on basal plane sapphire were determined using the anomalous dispersion effect of x-ray diffraction. Integrated intensities of three (00l) reflections were measured using the Lγ1 and Lβ2 excitation lines from a tungsten x-ray source. Calculations that included the effects of anomalous dispersion were compared with the measurements to identify the polarity. Each epitaxial layer had a single polarity rather than a mixture of oppositely polarized grains. However, both A- and B-oriented layers were observed. The method also provides a nondestructive estimate of the layer thickness.
Selective epitaxial growth of Si on sapphire using electron beam irradiation
Authors: Sawada Kazuaki , Ishida Makoto , Nakamura Tetsuro , Suzaki Tetso
Published: July 2002

A new selective epitaxial growth method of silicon on sapphire by disilane gas-source molecular beam epitaxy (MBE) is proposed. Selective epitaxial growth of Si films on sapphire was achieved by irradiation of an electron beam on the sapphire surface before Si MBE. Si was not deposited on the sapphire surface irradiated by an electron beam, and was grown epitaxially only on the nonirradiated area. The selective epitaxial growth was confirmed by optical micrographs, in situ reflection high-energy electron diffraction, and Auger electron spectroscopy. It was recognized by x-ray photoelectron spectroscopy that the sapphire surface was changed before and after electron beam irradiation: oxygen atoms on the sapphire surface were decreased due to irradiation of the electron beam and aluminum atoms mainly existed on the surface. This phenomenon can be considered to be the main cause of the selective epitaxial growth.
Investigation of cadmium-donor pairs in silicon
Authors: Achtziger N. , Deubler S. , Forkel D. , Wolf H. , Witthuhn W.
Published: July 2002

The formation of indium-donor pairs (donors: P, As, Sb) in silicon is identified by perturbed angular correlation spectroscopy. After the electron capture decay of the 111 In probe atoms to 111 Cd, the electric field gradient (EFG) is measured at the corresponding cadmium-donor pairs. For all three complexes a similar temperature dependence of the EFG is observed which can be explained quantitatively by a model based on the charge state of the cadmium-donor acceptors. The corresponding energy levels are given.
Zero resistance at 132 K in lead-free Bi1.9Sb0.1Sr2Ca2Cu3Oy
Authors: Chandrachood M. R. , Mulla I. S. , Sinha A. P. B.
Published: July 2002

Zero resistance has been observed at 132 K in a material which has a nominal composition of Bi1.9Sb0.1Sr2Ca2Cu3Oy. X-ray results suggest predominance of the 2:2:2:3 phase but the well known transition at 105–110 K is absent, which apparently has been enhanced to 132 K.
Synthesis of YBa2Cu3O7−x from a soluble Y-Ba-Cu precursor
Authors: Rupich M. W. , Lagos B. , Hachey J. P.
Published: July 2002

The synthesis of the superconducting YBa2Cu3O7−x from a soluble, molecular precursor with the composition Cu3O3Ba2Y(meOEt)7 (meOEt is 2-methoxyethoxide) is described. The precursor was synthesized from the reaction of a soluble copper (II) oxide polymer with alkoxides of barium and yttrium. Pyrolysis and oxidation of the precursor resulted in the formation of oriented sheets of the orthorhombic YBa2Cu3O7−x phase. The orientation in the bulk YBa2Cu3O7−x is believed to result from the presence of linear Cu-O-Cu-O chains in the precursor. Bulk YBa2Cu3O7−x, prepared from the precursor, had an onset transition temperature of 92.5 K and zero resistance at 89.5 K.
Antiphase domain boundary formation in single-crystal chalcopyrite-structure ZnGeAs2 grown on GaAs
Authors: Solomon G. S. , Posthill J. B. , Timmons M. L.
Published: July 2002

Using transmission electron microscopy we have observed antiphase domain boundaries in single-crystal (001) ZnGeAs2 grown on vicinal (100) GaAs by organometallic vapor phase epitaxy. These antiphase domains boundaries pertain only to the cation sublattice of the chalcopyrite-structure ZnGeAs2 and are initiated at the heteroepitaxial interface because there exists a level of ordering on the cation sublattice in the ZnGeAs2 epitaxial film that is absent in the GaAs substrate. There are two possible types of displacement vectors characterizing these antiphase domain boundaries, and a zinc-blende-structure substrate orientation to eliminate the boundaries is suggested.
Passivation of defects in polycrystalline superlattices and quantum well structures
Authors: Tsu Raphael , Nicollian Edward H. , Reisman Arnold
Published: July 2002

In order to broaden the available materials for superlattices and quantum well structures, well-passivated polycrystalline semiconductors and amorphous oxides such as pc-Si/a-SiO2, pc-Ge/a-GeO2 (pc: polycrystalline; a: amorphous) are proposed. Crucial in maintaining long scattering length involves the passivation of pc-Si (polycrystalline silicon) and pc-Ge. Specific means to passivate grain boundaries are discussed which consist of the use of the common dangling bond teminator, hydrogen, as well as amorphous oxides and other amorphous materials. This unique procedure may be extended to the entire group III-V semiconductors such as polycrystalline GaAs and InP.
Identification of Pb-doped Bi-Sr-Ca-Cu-O superconducting phases by convergent beam electron diffraction
Authors: Fung K. K. , Yang C. Y. , Yan Y. F.
Published: July 2002

Pb-doped Bi2Sr2Ca2Cu3O10 (2223) and Bi2 Sr2 Ca3 Cu4 O12 (2234) superconducting phases have been identified by convergent beam electron diffraction. The c parameters of the 2223 and 2234 phases are 37.6 and 44 Å, respectively. The two phases have the same symmetry; their common point group is mmm. Both phases are modulated, but the modulations are different from and considerably weaker than that in the unleaded Bi2 Sr2 CaCu2 O8 . This work confirms for the first time the existence of the 2234 phase.
Dielectric properties of glasses prepared by quenching melts of superconducting Bi-Ca-Sr-Cu-O cuprates
Authors: Varma K. B. R. , Subbanna G. N. , Ramakrishnan T. V. , Rao C. N. R.
Published: July 2002

Glasses obtained from quenching melts of superconducting bismuth cuprates of the formula Bi2(Ca,Sr)n+1CunO2n+4 with n=1 and 3 exhibit novel dielectric properties. They possess relatively high dielectric constants as well as high electrical conductivity. The novel dielectric properties of these cuprate glasses are likely to be of electronic origin. They exhibit a weak microwave absorption due to the presence of microcrystallites.
Lattice site location of europium in LiNbO3 by Rutherford backscattering channeling experiments
Authors: Rebouta L. , Soares J. C. , da Silva M. F. , Sanz-García J. A. , Diéguez E. , Agulló-López F.
Published: July 2002

The lattice location of Eu3+ in LiNbO3 single crystals has been investigated by Rutherford backscattering channeling techniques. It has been concluded that Eu3+ lies partly at the Nb (64%) and Li (36%) sites but not at the intrinsic vacant site.
Microstructure of epitaxially oriented superconducting YBa2Cu3O7−x films grown on (100) MgO by metalorganic decomposition
Authors: Lee S.-Tong , Chen Samuel , Hung L. S. , Braunstein G.
Published: July 2002

The microstructure in epitaxially oriented thin films of YBa2Cu3O7−x grown on (100) MgO by metalorganic decomposition has been studied by transmission electron microscopy and ion channeling. The as-prepared films consisted of single-crystal platelets lying flat on the MgO surface. The majority of the crystallites showed perfect alignment of their c axis with the [100] axis of MgO, while some crystallites were found to have a misorientation of up to 7.5°. Images of the interfacial regions showed good epitaxial growth to within one lattice spacing of the MgO substrate. He++ channeling measurements as a function of energy from 1 to 4.5 MeV indicated a 0.51° spread in crystallite orientation. Extrapolation of the channeling measurements to the limit of zero crystallite spread gave a minimum yield of 0.20 for bulk YBa2Cu3O7−x , which is much larger than the value reported for single crystals. The large backscattering yield is attributed to the grain boundaries in the film. A relatively strain-free interface was indicated by channeling results.
Stepwise-graded-index multilayer broadband low-reflectivity coating for AlGaAs/GaAs power lasers
Authors: Marclay E. , Webb D. J. , Buchmann P. , Vettiger P.
Published: July 2002

We describe a new type of optical low-reflectivity coating and its application to GaAs/AlGaAs power lasers. The low-reflectivity region of this coating extends over a broad wavelength range, therefore making the overall reflectivity much less sensitive to thickness variations as compared to single-layer coatings. In addition, only two materials (SiO2 and a-Si:H) are required, thus making it very easy to fabricate such coatings with standard deposition techniques such as plasma-enhanced chemical vapor deposition (PECVD) or ion beam sputtering. Finally, the optical quality of coatings deposited by PECVD was confirmed by measurements on power lasers, showing optical power outputs in excess of 60 W/mm, among the highest reported value for coated mirrors.
Dehydrogenation—a simple method of synthesizing metallic glasses
Authors: Tsai Rung-Ywan , Wu Shinn-Tyan
Published: July 2002

Vacuum dehydrogenation of a crystalline phase CrHxCyOz results in an amorphous phase. The crystalline phase is prepared by electroplating from a cold chromic acid electrolyte with formic acid as additive.
Silicon crystallite formation in ion-implanted quartz
Authors: Ramabadran Uma B. , Jackson Howard E. , Farlow G. C.
Published: July 2002

Rapid thermally annealed silicon-implanted x-cut α-quartz samples have been examined by Rutherford backscattering and Raman microprobe spectroscopy. The data indicate that the silicon has diffused at 1200 °C to form a buried layer of crystallites of size 1–10 μm. The crystallites are preferentially oriented and under substantial stress.
Composition dependence of high T
c phase formation in Pb-doped Bi-Sr-Ca-Cu-O thin films
Authors: Tanaka Atsushi , Kamehara Nobuo , Niwa Koichi
Published: July 2002

We studied the composition dependence of high Tc phase Bi2Sr2Ca2Cu3Ox formation in Pb-doped Bi system thin films. Films were prepared by rf magnetron sputtering using three targets and post-annealed to synthesize superconducting films. In addition to a Bi-Sr-Ca-Cu-O target, PbO and CuO targets were used to dope sufficient Pb into the films and to optimize the Cu content. Although heavily Pb-doped thin films form the high Tc phase rapidly, they are multiphased and have poor morphology. The Cu content decreases slightly during sintering. Minimizing the amount of doped Pb needed for the high Tc phase formation improves morphology, and slightly Cu-rich composition is effective in forming the high Tc phase. Nearly single-phase high Tc films were obtained from the as-deposited compositions of Bi:Pb:Sr:Ca:Cu=1.02:0.80:1.00:0.99:1.64 after only one hour of sintering in air at 851 °C. The single-phase high Tc film forms in a very narrow sintering temperature range.
Selective and stoichiometric reaction of copper dipivaloylmethanate [Cu(DPM)2] with surface hydroxyls on SiO2
Authors: Sekine Rika , Kawai Maki
Published: July 2002

Stoichiometric reaction of copper dipivaloylmethanate [Cu(DPM)2] with the hydroxyl group (OH) on SiO2 surface was studied by infrared spectroscopy. The stoichiometric ratio of reacted OH and Cu(DPM)2 was estimated to be ∼2–3:1 from the absorbance of the OH and the CH stretching region. The ligand DPM was removed from the SiO2 surface by treatment with water at 400 °C. The oxidation state of Cu remaining on the surface was proven to be +1 by x-ray photoelectron spectroscopy.
Growth of CdTe by organometallic vapor phase epitaxy in an impinging jet reactor
Authors: Snyder D. W. , Ko E. I. , Sides P. J. , Mahajan S.
Published: July 2002

Deposition of (100)CdTe epilayers by organometallic vapor phase epitaxy (OMVPE) has been investigated using a vertical downward flowing impinging jet reactor with dimethylcadmium (DMCd) and diethyltelluride (DETe) as the organometallic sources. An Arrhenius plot of deposition rate versus substrate temperature had a linear region over a wide temperature range from 320 to 480 °C, corresponding to an activation energy for growth of 18 kcal/mol. Surfaces of (100)CdTe epilayers had high densities of pyramidal hillocks. Double-crystal x-ray rocking curves, however, were not affected by the presence of the hillocks. Full widths at half maximum for the (400) reflection of less than 30 arcsec were obtained for growth temperatures from 400 to 480 °C. At 460 °C rocking curves for the epilayer were nearly identical to the substrate demonstrating that films whose quality matches that of the underlying substrate can be deposited in the impinging jet system.
Transmission mode spatial light modulator using a B12SiO20 crystal and polymer-dispersed liquid-crystal layers
Authors: Takizawa Kuniharu , Kikuchi Hiroshi , Fujikake Hideo , Okada Masakatsu
Published: July 2002

We describe a new type of transmission mode spatial light modulator (SLM) using a photoconductive Bi12SiO20 crystal and a polymer-dispersed liquid crystal (PDLC) composed of microdroplets of nematic liquid crystal of nonspherical shape randomly dispersed in polymer matrix. The SLM using light scattering in the PDLC has several advantages, such as no polarizer, high transmission of readout light, video rate operation, and ease of fabrication. The device, which consists of a 20 μm PDLC and a 0.5 mm Bi12SiO20 crystal, has a limiting resolution of 30 lp/mm and a high uniformity of the readout image.
Acoustic microscopy at 15.3 GHz in pressurized superfluid helium
Authors: Muha M. S. , Moulthrop A. A. , Kozlowski G. C. , Hadimioglu B.
Published: July 2002

An acoustic microscope operating at 15.3 GHz and using superfluid 4He as the coupling medium has been developed. The helium is colder than 0.9 K to achieve low acoustic attenuation, and is pressurized to greater than 20 bar to eliminate three-phonon processes which saturate the received signal as the input power is increased. A resolution of 150 Å has been achieved.
Anisotropy of the linear and third-order nonlinear optical properties of a stretch-oriented polymer film of poly-[2, 5-dimethoxy paraphenylenevinylene]
Authors: Swiatkiewicz Jacek , Prasad Paras N. , Karasz Frank E. , Druy Mark A. , Glatkowski Paul
Published: July 2002

Large linear refractive index birefringence, strong dichroic behavior, and highly anisotropic χ(3) have been observed for a uniaxially oriented poly (2, 5-dimethoxy paraphenylene vinylene) film. A subpicosecond time-resolved degenerate four-wave mixing study reveals an unusual behavior. Along the draw direction χ(3) is complex with a negative real part and has a response time that is longer than the optical pulse resolution. In contrast, χ(3) along the transverse direction is largely real and positive. Its response time is much faster, and is limited by the laser pulse width of ∼400 fs.
Evaluation of carrier distributions in a depletion region of semiconductor measured by a capacitance-voltage profile method
Authors: Yeo Y. K. , Gainer G. H. , Kim Jong Hyun , Hengehold R. L.
Published: July 2002

It is well known that carrier depth profiles obtained by the capacitance-voltage (C-V) measurement method provide carrier information only beyond the initial semiconductor depletion region. A novel new method has been developed within the depletion approximation for obtaining carrier depth profiles inside the initial depletion region of a semiconductor through the combined use of the layer-removal technique and C-V profile measurements. This method has been successfully demonstrated through simulated C-V profile data created from a known Gaussian distribution of Si-implanted GaAs.
Biomolecular/solid-state nanoheterostructures
Authors: Douglas Kenneth , Clark Noel A. , Rothschild Kenneth J.
Published: July 2002

We demonstrate a fabrication process for making composite biological/solid-state heterostructures of nanometer dimension (nanoheterostructures). In this process individual protein molecules selectively self-assemble onto a 1.2-nm-thick Ta/W oxide film which has been patterned into a screen-like lattice with holes of 22 nm periodicity by parallel nanometer molecular lithography. Self-assembly is accomplished by preferential electrostatic bonding of the protein molecules to selected sites on the solid-state lattice.
Measurement of homogeneously broadened spectra of spontaneous emission and small-signal gain in a low-energy, waveguide-mode free-electron laser
Authors: Lee Byung Cheol , Kawamura Yoshiyuki , Toyoda Koichi , Kawai Masayuki , Lee Sang Soo
Published: July 2002

The spontaneous emission spectrum and the small-signal gain have been measured in a low-energy, waveguide-mode free-electron laser. Measurements are carried out at microwave frequencies (25–40 GHz) in an X-band rectangular waveguide with a low-energy (450–600 keV, γ∼2), low-current (∼1.5 A), low-energy spread (ΔE/E≪10−4) relativistic photoelectron beam. The measured spontaneous emission spectrum agrees well with the homogeneously broadened spectrum of the TE10 waveguide mode. The measured small-signal gain spectrum is in good agreement with the theoretical prediction calculated under the assumption of operation in the low-gain Compton regime.
Scanning tunneling microscopy of [112̄] oriented steps on a cleaved Si(111) surface
Authors: Tokumoto Hiroshi , Wakiyama Shigeru , Miki Kazushi , Okayama Shigeo
Published: July 2002

Scanning tunneling microscopy on cleaved Si(111) surfaces reveals stress-induced microstructures with two types of terraces: triangular-shaped terraces and long and narrow terraces with parallel [112̄] oriented steps, which is contrary to the previous observation [1̄1̄2] steps. Dimer rows in Si(111) 2×1 structures are found on the triangular terraces. On the parallel-stepped terraces, rows run in the [112̄] direction and their separation was appreciably smaller than that of the dimer rows in the 2×1 structure. A new model for this structure is proposed.