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19 Oct 1987

Volume 51, Issue 16, pp. 1209-1288

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Electronic optical bistability in a GaAs/AlGaAs strip‐loaded waveguide

M. Warren, W. Gibbons, K. Komatsu, D. Sarid, D. Hendricks, H. M. Gibbs, and M. Sugimoto

Appl. Phys. Lett. 51, 1209 (1987); http://dx.doi.org/10.1063/1.99002 (3 pages) | Cited 14 times

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Optical bistability of electronic origin has been observed in strip‐loaded waveguides in a GaAs/AlGaAs multiple quantum well structure. Single‐mode waveguides were fabricated by reactive ion etching of an epitaxial AlGaAs layer above the quantum wells. The waveguides were operated as nonlinear Fabry–Perot étalons with 30% reflectors provided by the cleaved ends. Phase shifts of 2π were observed in some devices.
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42.79.Gn Optical waveguides and couplers
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
42.65.Pc Optical bistability, multistability, and switching, including local field effects

High power, high efficient neodymium:yttrium aluminum garnet laser end pumped by a laser diode array

Josef Berger, David F. Welch, Don R. Scifres, William Streifer, and Peter S. Cross

Appl. Phys. Lett. 51, 1212 (1987); http://dx.doi.org/10.1063/1.98733 (3 pages) | Cited 22 times

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We report the highest electrical to optical conversion efficiency, 10.8%, at 415 mW cw, 1.06 μm, from a neodymium:yttrium aluminum garnet end pumped by a monolithic, 200‐μm‐wide laser diode array. The highest cw output powers up to 465 mW are achieved. The beam profile is TEM00 at all power levels.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Fast optical switching and optical bistability in a PbSnSe étalon

J. J. E. Reid, A. K. Kar, H. A. MacKenzie, P. L. Chua, R. Grisar, and H. M. Preier

Appl. Phys. Lett. 51, 1215 (1987); http://dx.doi.org/10.1063/1.98734 (3 pages) | Cited 5 times

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We report the observation of optical bistability with nanosecond optical switching in the lead chalcogenide semiconductor Pb1−xSnxSe. The observed refractive optical nonlinearities were generated by the absorption of radiation from a pulsed CO2 laser at incident intensities of 80 kW cm−2.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
81.40.Tv Optical and dielectric properties related to treatment conditions
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Simultaneous, multiple wavelength lasing of (Er, Nd):Y3Al5O12

W. Q. Shi, R. Kurtz, J. Machan, M. Bass, M. Birnbaum, and M. Kokta

Appl. Phys. Lett. 51, 1218 (1987); http://dx.doi.org/10.1063/1.98735 (3 pages) | Cited 32 times

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Simultaneous lasing of both Er3+ and Nd3+ ions in yttrium aluminum garnet is reported. The crystal was doped with 15% Er3+ and 1% Nd3+ ions. The Er3+ ions lased at 2.94 μm and the Nd3+ ions in a broadband from 1.01 to 1.15 μm with a strong peak at 1.064 μm. Significant ion‐ion interaction is suggested by the drastically altered fluorescent lifetimes and unusual lasing properties.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.45.+h Stimulated emission

Elimination of birefringence in garnet films for magneto‐optic waveguide devices

R. Wolfe, V. J. Fratello, and M. McGlashan‐Powell

Appl. Phys. Lett. 51, 1221 (1987); http://dx.doi.org/10.1063/1.98736 (3 pages) | Cited 26 times

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The linear birefringence of magneto‐optic garnet thin films, which interferes with the Faraday rotation in waveguide devices, can be reduced to small values by growing multilayer films to minimize the shape effect, annealing at high temperatures to reduce the growth‐induced effect, and growing the films in compression to control the photoelastic effect. The remaining birefringence can be reduced to zero by chemically etching the film until the effects exactly cancel each other at a particular wavelength. This etch‐tuning procedure is demonstrated on a two‐layer bismuth‐yttrium iron garnet (Bi‐YIG) film at wavelengths of 1.51 and 1.32 μm. Extinction ratios of 100 to 1 have been achieved at 45° and 90° Faraday rotations at both wavelengths.
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78.66.-w Optical properties of specific thin films
42.79.Gn Optical waveguides and couplers
85.70.Ge Ferrite and garnet devices

Spectral evolution in an electron beam pumped XeF laser

D. G. Harris, D. H. Burde, R. J. Malins, and J. H. Tillotson

Appl. Phys. Lett. 51, 1224 (1987); http://dx.doi.org/10.1063/1.98737 (3 pages) | Cited 2 times

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A spectral sweep in the 353‐nm band of an electron beam pumped XeF laser has been investigated. The time‐integrated lasing spectra broaden as the pulse length, electron beam pump rate, and intracavity flux are increased. Several possible explanations are discussed.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Oxide conductive coated cathodes for a sealed‐off CO2 laser

Tai‐Chiung Hsieh and Yuan‐Liang Lan

Appl. Phys. Lett. 51, 1227 (1987); http://dx.doi.org/10.1063/1.98738 (3 pages) | Cited 4 times

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Cold cathodes coated with oxide conductive materials, such as indium tin oxide and tin oxide, were applied to dc gas discharges of a sealed‐off CO2 laser. Laser power enhancement and stable gas discharge, two areas of laser performance, were affected, in contrast to the uncoated metallic cathode. Mass spectrometric study revealed a correlation of laser power enhancement and an increase in the CO2 content associated with these coated cathodes.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
52.80.-s Electric discharges

Digital optical switch

Y. Silberberg, P. Perlmutter, and J. E. Baran

Appl. Phys. Lett. 51, 1230 (1987); http://dx.doi.org/10.1063/1.98739 (3 pages) | Cited 58 times

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We propose and demonstrate a novel polarization‐ and wavelength‐independent digital electro‐optic switch in Ti:LiNbO3. This four‐port integrated optics switch is characterized by a steplike response to the applied voltage. Switching is achieved through adiabatic eigenmode transformation in an asymmetric waveguide junction. We demonstrate switching of both polarization components at two wavelengths (1.32 and 1.52 μm) with a crosstalk of −20 dB.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.-m Integrated optics
78.20.Jq Electro-optical effects
42.79.Gn Optical waveguides and couplers

High‐speed light valve using an amorphous silicon photosensor and ferroelectric liquid crystals

N. Shin‐ichi Takahashi, Hideki Asada, Masaki Miyahara, Shoichi Kurita, and Hiroyuki Kuriyama

Appl. Phys. Lett. 51, 1233 (1987); http://dx.doi.org/10.1063/1.98740 (3 pages) | Cited 7 times

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A novel high‐speed response light valve composed of a hydrogenated amorphous silicon (a‐Si:H) photosensor and a chiral smectic C phase liquid crystal is presented for the first time. This device is optically addressed. The switching between on and off states is caused by reversing the polarity of the applied voltage across the liquid crystal due to the photocurrent from the a‐Si photosensor. The response time measured is about 400 μs. The switching speed of this device is one to two orders of magnitude faster than that of the nematic liquid‐crystal light valve. This device can be applied to optical bistable devices without optical feedback, using an electro‐optic memory effect of the ferroelectric liquid crystal.
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42.79.Hp Optical processors, correlators, and modulators
85.60.Pg Display systems
78.20.Jq Electro-optical effects
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Enhanced Cu‐Teflon adhesion by presputtering treatment: Effect of surface morphology changes

Chin‐An Chang

Appl. Phys. Lett. 51, 1236 (1987); http://dx.doi.org/10.1063/1.98741 (3 pages) | Cited 28 times

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The recently observed enhancement in adhesion between Cu and Teflon due to a presputtering treatment of Teflon prior to the Cu deposition is analyzed. The sputtering treatment resulted in a morphology change of the Teflon, with the deposited Cu showing similar textures, and changes in chemical bondings between the two. A simple geometric model is used to analyze the contribution from the morphology changes to the observed peel strength. It is shown that, for a finite chemical bonding, an appreciable contribution to the peel strength is possible from the morphology changes observed.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.-b Surface treatments
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Defects in (111) HgTe grown by molecular beam epitaxy

R. D. Feldman, S. Nakahara, R. F. Austin, T. Boone, R. L. Opila, and A. S. Wynn

Appl. Phys. Lett. 51, 1239 (1987); http://dx.doi.org/10.1063/1.98742 (3 pages) | Cited 10 times

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Room‐temperature Hall mobilities of (100) HgTe films grown by molecular beam epitaxy can reach values of 27 000–31 000 cm2 V−1 s−1, while the mobilities of (111) films are only 14 000–16 000 cm2 V−1 s−1. We show that the defects which lead to the lower mobilities of (111) films are present in the first 1000 Å of growth. Transmission electron microscope studies reveal a cellular structure of high‐angle grain boundaries with some twinning about the (111) growth axis. These defects, and hence the reduced mobilities of the films, appear to result from island nucleation of the films.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ga II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Bias dependence of instability mechanisms in amorphous silicon thin‐film transistors

M. J. Powell, C. van Berkel, I. D. French, and D. H. Nicholls

Appl. Phys. Lett. 51, 1242 (1987); http://dx.doi.org/10.1063/1.98692 (3 pages) | Cited 86 times

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We have measured the bias dependence of the threshold voltage shift in a series of amorphous silicon‐silicon nitride thin‐film transistors, where the composition of the nitride is varied. There are two distinct instability mechanisms: a slow increase in the density of metastable fast states and charge trapping in slow states. State creation dominates at low fields and charge trapping dominates at higher fields. The state creation is found to be independent of the nitride composition, whereas the charge trapping depends strongly on the nitride composition. This is taken as good evidence that state creation takes place in the hydrogenated amorphous silicon (a‐Si:H) layer, whereas the charge trapping takes place in the a‐SiN:H. The metastable states are suggested to be Si dangling bonds in the a‐Si:H, and the state creation process similar to the Staebler–Wronski effect. The confirmation of state creation in a thin‐film transistor means that states can be created simply by populating conduction‐band states in the undoped material. The slow states are also thought to be Si dangling bonds, but located in the silicon nitride matrix.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

New hydride vapor phase epitaxy for GaP growth on Si

H. Mori, M. Ogasawara, M. Yamamoto, and M. Tachikawa

Appl. Phys. Lett. 51, 1245 (1987); http://dx.doi.org/10.1063/1.98693 (3 pages) | Cited 15 times

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Gallium phosphide films are successfully grown on (100) Si substrates by a new hydride vapor phase epitaxy. Mixing of reactant vapors just above the substrate makes the growth rate as high as 50 nm/min even in the temperature range of 350–450 °C. This makes the two‐step growth procedure applicable for growing a single domain GaP film on Si from H2‐HCl‐PH3‐Ga reactants. An etch pit density of 7.5×106 cm−2 and a full width at half‐maximum of 93 arcsec in a double‐crystal x‐ray rocking curve are achieved. Green light‐emitting diodes with 565 nm peak wavelength are successfully fabricated using nitrogen‐doped GaP films grown on Si.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.61.Ey III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.60.Jb Light-emitting devices

Model calculation on the Meyer–Neldel rule for the field‐effect conductance of hydrogenated amorphous silicon

Byung‐Gook Yoon and Choochon Lee

Appl. Phys. Lett. 51, 1248 (1987); http://dx.doi.org/10.1063/1.98694 (3 pages) | Cited 2 times

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A model calculation was carried out to study the Meyer–Neldel rule of the field‐effect conductance of hydrogenated amorphous silicon (a‐Si:H). It was found that the shift of Fermi level and the potential profile in the sample with temperature can explain the Meyer–Neldel rule if a model density of states of a‐Si:H is properly chosen. So it is of doubt to think that the conductivity prefactor varies in a single sample of band‐bending case, as assumed by some authors.
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73.50.Dn Low-field transport and mobility; piezoresistance
73.20.At Surface states, band structure, electron density of states
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Rapid thermal anneal induced effects in polycrystalline silicon gate structures

Avid Kamgar and S. J. Hillenius

Appl. Phys. Lett. 51, 1251 (1987); http://dx.doi.org/10.1063/1.98695 (3 pages) | Cited 12 times

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Effects of dynamic temperature nonuniformities during rapid thermal anneal (RTA) cycles of layered structures have been investigated. Silicon gate capacitors (4000 Å, As doped, polycrystalline Si on 175 Å thermal oxide) were subjected to temperatures 450–1200 °C using incoherent radiation from W lamps. Capacitance‐voltage measurements before and after RTA showed that due to RTA, interface traps were generated at temperatures as low as 600 °C, but that they were passivated by a standard post‐metallization anneal. High‐temperature RTA induced, in addition, a residual flatband voltage shift which was not removed by hydrogen anneal. The residual shift can be due to either a change in oxide fixed charges or changes in the characteristics of the polycrystalline Si gate. Faster temperature ramp rates increased the generation of interface traps confirming the dynamic nature of stress, but did not affect the residual shift.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Enhanced ballistic transport in InGaAs/InAlAs hot‐electron transistors

J. Chen, U. K. Reddy, D. Mui, C. K. Peng, and H. Morkoç

Appl. Phys. Lett. 51, 1254 (1987); http://dx.doi.org/10.1063/1.98696 (2 pages) | Cited 1 time

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Hot‐electron transistors fabricated using a 600‐Å InGaAs base and a 500‐Å InAlAs barrier have shown a peak ballistic common base current gain of 0.82 at 77 K despite the large injection energies. Reduction of injection energies by lowering the emitter and collector barriers should lead to an even higher ballistic transport ratio due to the reduced Γ‐L scattering.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
73.50.Fq High-field and nonlinear effects

Subboundary‐free zone‐melt recrystallization of thin‐film silicon

Loren Pfeiffer, A. E. Gelman, K. A. Jackson, K. W. West, and J. L. Batstone

Appl. Phys. Lett. 51, 1256 (1987); http://dx.doi.org/10.1063/1.98697 (3 pages) | Cited 24 times

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Scanned zone‐melt recrystallization (ZMR) of amorphous Si 1‐μm films on SiO2 results in subboundary‐free material provided the thermal gradient along the scan is reduced to 4 K/mm or less. Below this value the usual ZMR subboundaries consisting of networks of in‐plane edge dislocations are replaced by rows of threading dislocations. We account for the two kinds of crystallization by extending the faceted solidification model that we developed previously. We consider profiles of the solidification front at the intersections of {111} facet pairs where subboundaries are known to form, and postulate that the profiles are aligned approximately normal to the scan in the high gradient case, but become tilted toward the plane of the SiO2 cap layer for the low gradient case. The tilting accounts in a natural way for subboundary removal and the transition from in‐plane to threading dislocations.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.10.Fq Growth from melts; zone melting and refining
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Carrier transport property in the amorphous silicon/amorphous silicon carbide multilayer studied by the transient grating technique

K. Hattori, T. Mori, H. Okamoto, and Y. Hamakawa

Appl. Phys. Lett. 51, 1259 (1987); http://dx.doi.org/10.1063/1.98698 (3 pages) | Cited 16 times

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The in‐plane diffusion coefficient and lifetime of photogenerated carriers in amorphous silicon have been measured by the transient grating technique in amorphous silicon (a‐Si)/silicon carbide (a‐SiC) multilayered structures, as a function of the a‐Si well layer thickness. As the layer thickness is decreased, the diffusion coefficient gradually decreases, while the lifetime drastically increases by more than one order of magnitude than that in thick unlayered a‐Si. These behaviors suggest that the carrier transport is determined both by carrier interaction with shallow traps at a‐Si/a‐SiC interfaces and by quantum‐size effect through weakened carrier coupling with deep states.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.-r Electrical properties of specific thin films
72.80.Ng Disordered solids

Effects of trichloroethane during oxide growth on radiation‐induced interface traps in Metal/SiO2/Si capacitors

Eronides F. da Silva, Yasushiro Nishioka, and T.‐P. Ma

Appl. Phys. Lett. 51, 1262 (1987); http://dx.doi.org/10.1063/1.98699 (3 pages) | Cited 3 times

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The radiation‐induced interface traps in Metal/SiO2/Si capacitors where the oxides are grown in dry O2+1.1.1.‐trichloroethane (TCA) have been studied. Among all the samples tested, a peak in the interface trap distribution above midgap (centered at ∼Eν +0.70–0.75 eV) appears immediately after irradiation, and the magnitude of this peak is a function of the amount of TCA during oxide growth. After the termination of the irradiation, this peak will either increase or decrease with time at room temperature for a few hours, followed by a continuous decrease over a long period of time (up to several months) before saturation, and this time‐dependent behavior also appears to be a function of the TCA concentration. In the case when this peak decreases with time, a second peak located below midgap (centered at ∼Eν +0.35 eV) will develop, and the rate of growth of the second peak is correlatable to the reduction of the first peak. A closer examination of the data reveals that it is the initial damage level that determines the post‐radiation time‐dependent behavior, and the apparent dependence on the TCA concentration arises from its effect on the radiation sensitivity of the SiO2/Si interface.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Fe Electron and positron radiation effects
61.80.Cb X-ray effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Thermal conversion of AlxGa1−xAs layers grown by molecular beam epitaxy

Sadao Adachi and Shoji Yamahata

Appl. Phys. Lett. 51, 1265 (1987); http://dx.doi.org/10.1063/1.98700 (3 pages) | Cited 4 times

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We report the observation of thermal conversion of AlxGa1−xAs alloys grown by molecular beam epitaxy (MBE) from undoped, high‐resistivity AlxGa1−xAs to low‐resistivity, p‐type material after annealing beyond the growth temperature (∼650 °C). The phenomenon occurs only in the Al‐containing layers and not in the GaAs. Electrical measurements indicate that a substantial concentration of residual C acceptors causes the thermal conversion of the AlxGa1−xAs layers. A possible mechanism of C incorporation during MBE is examined from a thermodynamical point of view.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Biaxially stressed excitons in GaAs/AlGaAs quantum wells grown on Si substrates

C. Jagannath, S. Zemon, P. Norris, and B. S. Elman

Appl. Phys. Lett. 51, 1268 (1987); http://dx.doi.org/10.1063/1.98701 (3 pages) | Cited 16 times

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Photoluminescence and photoluminescence excitation spectroscopies are utilized to study excitons in GaAs/AlGaAs quantum wells (QW’s) fabricated by molecular beam epitaxy on a GaAs buffer layer grown on a Si substrate. The buffer layer was grown by metalorganic vapor phase epitaxy. The experimental results are understood in terms of a uniform biaxial tension of approximately 3 kbar present in the plane of growth for both the QW’s and the GaAs buffer. An important consequence of the biaxial tension is that for QW’s with well widths larger than ≊15 nm the light‐hole and heavy‐hole subbands cross each other in energy, resulting in a light‐hole exciton energy lower than that of the heavy‐hole exciton, opposite to the case of QW’s grown on GaAs substrates.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Stability of 300 K continuous operation of p‐n AlxGa1−xAs‐GaAs quantum well lasers grown on Si

D. G. Deppe, D. W. Nam, N. Holonyak, K. C. Hsieh, R. J. Matyi, H. Shichijo, J. E. Epler, and H. F. Chung

Appl. Phys. Lett. 51, 1271 (1987); http://dx.doi.org/10.1063/1.98702 (3 pages) | Cited 31 times

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Data are presented on p‐n (diode) AlxGa1−xAs‐GaAs quantum well lasers grown on Si indicating that continuous 300 K operation is possible for four or more hours. Lower threshold diodes (1.4 kA/cm2) of given dislocation density are not necessarily as stable as higher threshold diodes (1.8 kA/cm2) of lower dislocation density, ∼10 min vs ≳4 h. Stability data on diodes agree with the behavior of photopumped samples of the same crystals with the Si substrates removed.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Excimer laser in situ treatment of GaAs surfaces: Electrical properties of tungsten/GaAs diodes

P. A. Maki and D. J. Ehrlich

Appl. Phys. Lett. 51, 1274 (1987); http://dx.doi.org/10.1063/1.98703 (3 pages) | Cited 1 time

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The effects of low‐power irradiation of an n‐type GaAs surface by a 193‐nm excimer laser during tungsten metallization have been examined. Schottky diode characteristics of surfaces held under ultrahigh vacuum (10−9 Torr) conditions and in oxygen and chlorine ambients of 10−6 Torr show significant shifts in effective barrier height due to irradiation and depending on the ambient. The results of the electrical measurements are interpreted in terms of the possible laser surface chemistry. The applications for in situ surface cleaning for device processing within a vacuum GaAs growth chamber and applications for laser photochemical etching and oxidation of GaAs are discussed.
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81.65.-b Surface treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
85.30.De Semiconductor-device characterization, design, and modeling
73.30.+y Surface double layers, Schottky barriers, and work functions

Synthesis of superconducting films of the Y‐Ba‐Cu‐O system by a screen printing method

R. C. Budhani, Sing‐Mo H. Tzeng, H. J. Doerr, and R. F. Bunshah

Appl. Phys. Lett. 51, 1277 (1987); http://dx.doi.org/10.1063/1.98704 (3 pages) | Cited 39 times

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A screen printing method has been used to deposit superconducting films of Y‐Ba‐Cu‐O materials on Al2O3 substrates. The electrical resistivity, microstructure, and adhesion of these films are highly sensitive to the post‐printing heat treatment. Films heat treated at 950 °C and below are poorly adherent, whereas those annealed above 1000 °C undergo phase separation to Y2Cu2O5 and BaCuO2 and also react with the substrate. Nearly single phase, highly adherent, and smooth films showing a zero resistance state at 79 K have been synthesized by optimizing the annealing conditions.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
74.78.-w Superconducting films and low-dimensional structures

Giant magnetic coercivity and percolation effects in granular Fe‐(SiO2) solids

Gang Xiao and C. L. Chien

Appl. Phys. Lett. 51, 1280 (1987); http://dx.doi.org/10.1063/1.98705 (3 pages) | Cited 97 times

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We demonstrate a novel method for enhancing the coercivity of magnetic materials. Granular Fe‐(SiO2) solids have been fabricated over a wide volume fraction range from 15% to 100%. Giant magnetic coercivity, as high as 2500 Oe, has been observed in granular solids in which the isolated Fe granules are only nanometers in size. Across the whole volume fraction range magnetic coercivity experiences dramatic variations due to the change of granular size and percolation effects.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Vv High coercivity materials
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