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13 Jun 1988

Volume 52, Issue 24, pp. 2013-2090

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All‐optical switching between modes of a GaAs/GaAlAs multiple quantum well waveguide

P. Li Kam Wa, P. N. Robson, J. S. Roberts, M. A. Pate, and J. P. R. David

Appl. Phys. Lett. 52, 2013 (1988); http://dx.doi.org/10.1063/1.99583 (2 pages) | Cited 7 times

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A strain‐induced multiple quantum well waveguide which can support two transverse modes in the plane normal to the quantum wells was excited in the TE mode by 350‐ns‐long probe pulses of low intensity from a dye laser tuned to a wavelength of 886 nm. A laser diode emitting at 850 nm was used in order to switch the 886 nm light between two positions at the exit facet of this overmoded waveguide. The switching mechanism has been shown to be non‐thermal in origin.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
42.79.Gn Optical waveguides and couplers
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Experimental determination of the relation between modal gain and current density for AlGaAs single quantum well lasers grown by metalorganic vapor phase epitaxy

S. H. Hagen, H. F. J. van ’t Blik, M. J. B. Boermans, and R. Eppenga

Appl. Phys. Lett. 52, 2015 (1988); http://dx.doi.org/10.1063/1.99567 (2 pages) | Cited 6 times

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The relation between modal gain and current density has been determined for a 20 Å single quantum well in a graded‐index separate‐confinement heterostructure laser. The measurements were performed at 153 K in order to avoid leakage of carriers out of the wells which might cause an apparent saturation of the gain. A sublinear dependence of gain on current density has been observed, agreeing rather well with theoretical calculations taking band mixing into account.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
85.60.Jb Light-emitting devices

Efficiency enhancement in quantum well lasers via tailored doping profiles

R. G. Waters, D. S. Hill, and S. L. Yellen

Appl. Phys. Lett. 52, 2017 (1988); http://dx.doi.org/10.1063/1.99568 (2 pages) | Cited 7 times

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Reduced doping concentrations proximate to the active region in single quantum well (Al)GaAs lasers have been used to improve the external quantum efficiency. A substantial enhancement is observed in a structure in which, by design, the mode overlap with the doped confining regions is large. For a structure in which the mode is tightly confined, doping modifications have no measurable effect.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
73.20.Hb Impurity and defect levels; energy states of adsorbed species
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Stark spectroscopic measurement of spatially resolved electric field and electric field gradients in a glow discharge

J. R. Shoemaker, B. N. Ganguly, and A. Garscadden

Appl. Phys. Lett. 52, 2019 (1988); http://dx.doi.org/10.1063/1.99569 (3 pages) | Cited 15 times

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Spatially resolved Stark spectra of triplet helium Rydberg states have been measured in the cathode fall region of a normal glow discharge. It is demonstrated that Stark spectral intensity distribution of a single Stark manifold provides both the electric field and the electric field gradient. The spectra of appropriate manifolds typically are sensitive to 20 V/cm change across the width of the probe laser beam. The experimental method of determining the electric field gradient locally means that one can measure space‐charge distributions in sheaths adjacent to electrodes, probes, and plasma boundaries.
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52.80.Hc Glow; corona
32.60.+i Zeeman and Stark effects
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.40.Mj Particle beam interactions in plasmas

Diagnostics of silane and germane radio frequency plasmas by coherent anti‐Stokes Raman spectroscopy

Joseph W. Perry, Y. H. Shing, and C. E. Allevato

Appl. Phys. Lett. 52, 2022 (1988); http://dx.doi.org/10.1063/1.99746 (3 pages) | Cited 5 times

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In situ plasma diagnostics using coherent anti‐Stokes Raman spectroscopy have shown different dissociation characteristics for GeH4 and SiH4 in radio frequency (rf) plasma‐enhanced chemical vapor deposition of amorphous silicon germanium alloy (a‐SiGe:H) thin films. The GeH4 dissociation rate in rf plasmas is a factor of about 3 larger than that of SiH4. Plasma diagnostics have revealed that the hydrogen dilution of the SiH4 and GeH4 mixed plasma plays a critical role in suppressing the gas phase polymerization and enhancing the GeH4 dissociation.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Surface, interface, and bulk properties of amorphous carbon films characterized by in situ ellipsometry

R. W. Collins

Appl. Phys. Lett. 52, 2025 (1988); http://dx.doi.org/10.1063/1.99570 (3 pages) | Cited 8 times

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Hydrogenated amorphous carbon film growth in diamond‐like and polymer‐like forms has been studied by in situ ellipsometry. The experiments provide accurate values of the optical functions, thickness, and deposition rate in real time. Reactions between the substrate and the gas phase species or film in the initial stages of growth, inaccessible to ex situ probes, have been detected with monolayer resolution. Monolayer changes in near‐surface bonding have also been detected.
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78.66.-w Optical properties of specific thin films
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.60.Fs Polarimeters and ellipsometers

Molecular beam epitaxy and metalorganic chemical vapor deposition growth of epitaxial CdTe on (100) GaAs/Si and (111) GaAs/Si substrates

A. Nouhi, G. Radhakrishnan, J. Katz, and K. Koliwad

Appl. Phys. Lett. 52, 2028 (1988); http://dx.doi.org/10.1063/1.99571 (3 pages) | Cited 14 times

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Epitaxial CdTe has been grown on both (100)GaAs/Si and (111)GaAs/Si substrates. A combination of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has been employed for the first time to achieve this growth: the GaAs layers are grown on Si substrates by MBE and the CdTe film is subsequently deposited on GaAs/Si by MOCVD. The grown layers have been characterized by x‐ray diffraction, scanning electron microscopy, and photoluminescence.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Diffuse scattering and superstructure reflections from In1−y(AlxGa1−x)yP

S. Yasuami, C. Nozaki, and Y. Ohba

Appl. Phys. Lett. 52, 2031 (1988); http://dx.doi.org/10.1063/1.99572 (3 pages) | Cited 21 times

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The structure of In1−y (Alx Ga1−x )y P semiconductor alloy systems was studied by electron diffraction. Varied distribution of diffuse scattering and superstructure reflections was observed. The pertinent ordered structure is dependent on growth parameters, but not on the alloy systems. The diffuse scattering could be attributed to mean square atomic displacements due to the coexistence of different column III atoms in the same sublattice.
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61.50.Ks Crystallographic aspects of phase transformations; pressure effects
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
61.66.Dk Alloys

Noise voltage and instability in GaAs devices

D. J. Day, M. Trudeau, S. P. McAlister, and C. M. Hurd

Appl. Phys. Lett. 52, 2034 (1988); http://dx.doi.org/10.1063/1.99573 (3 pages) | Cited 2 times

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Low‐frequency current noise that has a f−3/2 power law noise spectrum is observed in GaAs field‐effect devices. We show that this is due to modulation by a thermally activated and bias‐independent voltage noise in the gate. We identify this noise with generation recombination associated with the semi‐insulating substrate supporting these devices. Lowering the activation energy of these traps by the drain bias causes instability in this noise process, leading to low‐frequency oscillations that have previously been identified with high field domains in the substrate material.
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85.30.Tv Field effect devices
72.70.+m Noise processes and phenomena

Realization of high mobility in inverted AlxGa1−xAs/GaAs heterojunctions

N. M. Cho, D. J. Kim, A. Madhukar, P. G. Newman, D. D. Smith, T. Aucoin, and G. J. Iafrate

Appl. Phys. Lett. 52, 2037 (1988); http://dx.doi.org/10.1063/1.99574 (3 pages) | Cited 8 times

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We report reproducible realization of GaAs/Al0.25 Ga0.75 As(100) inverted heterojunctions with liquid‐nitrogen electron mobilities in excess of 105 cm2 /(V s). This is made possible through use of reflection high‐energy electron‐diffraction (RHEED) intensity dynamics determined optimized growth conditions, but without the use of short‐period superlattices as buffers or spacer layers.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Hi Surface barrier, boundary, and point contact devices

Substrate and capping layer effects on the phonon spectrum of ultrathin superlattices

D. J. Lockwood, M. W. C. Dharma‐wardana, G. C. Aers, and J.‐M. Baribeau

Appl. Phys. Lett. 52, 2040 (1988); http://dx.doi.org/10.1063/1.99747 (3 pages) | Cited 26 times

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GemSin ultrathin superlattices have been grown on (001) Si substrates and partly capped with Si. Raman scattering from acoustic phonons in the long‐wavelength region shows unexpectedly intense broad peaks that develop into an increased number of sharper intense peaks on capping. We identify these peaks with resonant phonon modes and use a linear chain model to expose the importance of substrate‐superlattice‐capping layer interactions in these multilayer structures.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.30.Hv Other nonmetallic inorganics
78.66.-w Optical properties of specific thin films
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Infrared detection of gaseous species during the filament‐assisted growth of diamond

F. G. Celii, P. E. Pehrsson, H.‐t. Wang, and J. E. Butler

Appl. Phys. Lett. 52, 2043 (1988); http://dx.doi.org/10.1063/1.99575 (3 pages) | Cited 165 times

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Infrared diode laser absorption spectroscopy is employed as an in situ method to examine gas phase species present during filament‐assisted deposition of diamond films. From a reactant mixture of 0.5% methane in hydrogen, methyl radical (CH3 ), acetylene (C2H2), and ethylene (C2H4 ) are detected above the growing surface, while ethane (C2H6 ), various C3 hydrocarbons, and methylene (CH2) radicals are below our sensitivity levels. The growth of polycrystalline diamond films on Si wafers and polycrystalline Ni is confirmed with x‐ray and Raman scattering, scanning electron microscopy, and Auger electron spectroscopy.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Oscillations in the optical response of (001)GaAs and AlGaAs surfaces during crystal growth by molecular beam epitaxy

J. P. Harbison, D. E. Aspnes, A. A. Studna, L. T. Florez, and M. K. Kelly

Appl. Phys. Lett. 52, 2046 (1988); http://dx.doi.org/10.1063/1.99576 (3 pages) | Cited 48 times

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Upon initiation of growth by molecular beam epitaxy, reflectance‐difference (RD) signals for (001)GaAs and AlAs surfaces exhibit a cyclic component that is periodic with (001) atomic bilayer coverage and that follows either surface structure or surface chemistry (coverage), depending on measurement wavelength. These RD oscillations may be phase shifted with respect to their reflection high‐energy electron diffraction counterparts, depending on deposition conditions.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Si p+‐n shallow junction fabrication using on‐axis Ga+ implantation

C‐M. Lin, A. J. Steckl, and T. P. Chow

Appl. Phys. Lett. 52, 2049 (1988); http://dx.doi.org/10.1063/1.99577 (3 pages) | Cited 5 times

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p+‐n shallow junction fabrication using on‐axis Ga implantation into crystalline and preamorphized Si, in conjuction with rapid thermal annealing, is reported. The implants are performed at energies of 50 and 75 keV for doses of 1 and 3.5×1015/cm2. Taking advantage of the short Ga projection range, low critical dosage (2×1014/cm2) needed for amorphizing the implanted layer, and a low anneal temperature (550–600 °C) required to induce solid phase epitaxial regrowth and activate the Ga dopants in excess of its maximum solid solubility in Si, a shallow junction at a depth of 100 nm and with sheet resistance of 150 Ω/☒ was obtained using 75 keV Ga implantation at a dose of 1×1015/cm2. The sheet resistance of the Ga‐implanted layer can be optimized by adjusting the anneal temperature and time.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.uf Ge and Si
85.40.Hp Lithography, masks and pattern transfer

Band bending and interface states for metals on GaAs

R. E. Viturro, J. L. Shaw, C. Mailhiot, L. J. Brillson, N. Tache, J. McKinley, G. Margaritondo, J. M. Woodall, P. D. Kirchner, G. D. Pettit, and S. L. Wright

Appl. Phys. Lett. 52, 2052 (1988); http://dx.doi.org/10.1063/1.99578 (3 pages) | Cited 35 times

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We have used soft x‐ray photoemission and optical emission spectroscopies to observe a broad range of Fermi level stabilization energies at metal interfaces with GaAs(100) surfaces grown by molecular beam epitaxy (MBE). The observed metal‐ and As‐related interface cathodoluminescence plus orders‐of‐magnitude differences in bulk‐defect‐related photoluminescence between melt‐ versus MBE‐grown GaAs suggest a role of bulk crystal growth and processing in controlling Schottky barrier formation.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.60.Hk Cathodoluminescence, ionoluminescence
73.30.+y Surface double layers, Schottky barriers, and work functions
78.55.Cr III-V semiconductors

Indium diffusion in the chemical potential gradient at an In0.53Ga0.47As/In0.52Al0.48As interface

R. J. Baird, T. J. Potter, G. P. Kothiyal, and P. K. Bhattacharya

Appl. Phys. Lett. 52, 2055 (1988); http://dx.doi.org/10.1063/1.99579 (3 pages) | Cited 19 times

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We have measured the distribution of group III metals at In0.53Ga0.47As/In0.52Al0.48As interfaces before and after annealing at 1085 K. We find little evidence for Al interdiffusion, but the Ga concentration profiles show some broadening on annealing. Also, the originally nearly constant In profiles develop strong modulations with near discontinuities at the original interfaces. This phenomenon is explained and modeled in terms of In diffusion in the chemical potential gradient established by the disparity of the Al and Ga mobilities and the requirement of III‐V stoichiometry in the alloys.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Dv Composition, segregation; defects and impurities

Dependence of the photoreflectance of semi‐insulating GaAs on temperature and pump chopping frequency

H. Shen, Z. Hang, S. H. Pan, Fred H. Pollak, and J. M. Woodall

Appl. Phys. Lett. 52, 2058 (1988); http://dx.doi.org/10.1063/1.99580 (3 pages) | Cited 32 times

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The amplitude of the photoreflectance (PR) spectra of the direct gap of semi‐insulating GaAs has been studied as a function of pump chopping frequency (2–4000 Hz) and temperature (25–198 °C). We have been able to deduce a temperature‐dependent trap time and hence trap activation energy of 0.70±0.05 eV. Our experiment demonstrates that PR can be used as a contactless method to study deep traps in semiconductors, analogous to deep level transient spectroscopy.
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78.20.Jq Electro-optical effects
71.55.Eq III-V semiconductors
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
FREE

Erratum: Silicon epitaxial growth on (100) patterned oxide wafers at 800 °C by ultralow‐pressure chemical vapor deposition [Appl. Phys. Lett. 52, 1797 (1988)]

Tri‐Rung Yew, Kenneth O, and Rafael Reif

Appl. Phys. Lett. 52, 2061 (1988); http://dx.doi.org/10.1063/1.99663 (3 pages) | Cited 2 times

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Abstract Unavailable
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Rh Phase transitions and critical phenomena
68.35.Fx Diffusion; interface formation
99.10.Cd Errata

Superconductivity and magnetic properties of high Tc Bi‐Sr‐Ca‐Cu‐O superconductors

H. Kumakura, K. Takahashi, D. R. Dietderich, K. Togano, and H. Maeda

Appl. Phys. Lett. 52, 2064 (1988); http://dx.doi.org/10.1063/1.99748 (2 pages) | Cited 7 times

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Magnetization measurements were performed at 77 K on Bi‐Sr‐Ca‐Cu‐O compounds having zero resistance temperatures at 103 and 82 K. The lower critical field Hc1 of the 103 K material was found to be 60% less than the Hc1 of YBa2Cu3O7. This suggests that the material has a higher Hc2 . The new compound also has less magnetization hysteresis than the YBa2Cu3O7 compound.
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74.10.+v Occurrence, potential candidates
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
74.25.Op Mixed states, critical fields, and surface sheaths

Observation of enhanced properties in samples of silver oxide doped YBa2Cu3Ox

P. N. Peters, R. C. Sisk, E. W. Urban, C. Y. Huang Development Division, and M. K. Wu

Appl. Phys. Lett. 52, 2066 (1988); http://dx.doi.org/10.1063/1.99775 (2 pages) | Cited 96 times

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Samples of YBa2 Cu3Ox doped with silver oxide (Tc ∼93 K) have exhibited attractive forces in gradient magnetic fields, both normal and tangential to the surfaces, which are more than twice the sample weight. This allows sample suspension below a rare earth magnet. Critical current density was increased by ∼102 at 77 K. Persistent fields, flux pinning, magnetization, and modeling are described.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates
74.25.Ha Magnetic properties including vortex structures and related phenomena

Characterization of thin films of Y‐Ba‐Cu‐O on oxidized silicon with a zirconia buffer layer

A. Mogro‐Campero, L. G. Turner, E. L. Hall, and M. C. Burrell

Appl. Phys. Lett. 52, 2068 (1988); http://dx.doi.org/10.1063/1.99749 (3 pages) | Cited 50 times

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Thin films of the high‐temperature superconductor Y‐Ba‐Cu‐O with zero‐resistance transition temperatures up to 83 K have been recently reported by using a zirconia buffer layer on the primary materials of interest for electronics, Si and SiO2. In this letter, various characteristics of these films are discussed. Microstructural analysis using transmission electron microscopy shows the complex morphology of the unoriented polycrystalline films. Elemental depth profiling by x‐ray photoelectron spectroscopy shows the effectiveness of the zirconia buffer layer in preventing interdiffusion; fluorine is found throughout the film at an abundance of 4 at. % The critical current density was measured as a function of temperature; its value is 5 kA cm−2 at 4.2 K.
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74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology

Scanning tunneling microscopy of the a‐b planes of Bi2(Ca,Sr)3Cu2O8+δ single crystal and thin film

M. D. Kirk, C. B. Eom, B. Oh, S. R. Spielman, M. R. Beasley, A. Kapitulnik, T. H. Geballe, and C. F. Quate

Appl. Phys. Lett. 52, 2071 (1988); http://dx.doi.org/10.1063/1.99750 (3 pages) | Cited 35 times

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A scanning tunneling microscope was used to image the a‐b plane of a single crystal of Bi2(Ca,Sr)3Cu2O8+δ (Tc∼85 K) and a thin film grown epitaxially on a (100) SrTiO3 substrate. Images taken at room temperature in air of a freshly cleaved bulk sample clearly show the one‐dimensional superstructure (27.2±0.7 Å periodicity) which is common to this phase. Several images show steps 16 Å high, suggesting that the cleavage occurs between 2122 molecular units. The registry of the superstructure from terrace to terrace is either shifted by half a superlattice parameter or is aligned. Images of evaporated thin films show features of comparable size, but not the same long‐range order as the crystal. Low‐temperature conductance measurements of the thin film exhibit a BCS‐like energy gap with 2Δ/kTc≊12.
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74.78.Fk Multilayers, superlattices, heterostructures
74.78.-w Superconducting films and low-dimensional structures
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology

High critical currents in Y‐Ba‐Cu‐O superconductors

S. Jin, T. H. Tiefel, R. C. Sherwood, M. E. Davis, R. B. van Dover, G. W. Kammlott, R. A. Fastnacht, and H. D. Keith

Appl. Phys. Lett. 52, 2074 (1988); http://dx.doi.org/10.1063/1.99751 (3 pages) | Cited 345 times

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Melt‐textured growth of polycrystalline YBa2Cu3O7−δ superconductor using directional solidification created an essentially 100% dense structure consisting of long, needle‐ or plate‐shaped crystals preferentially aligned parallel to the a‐b conduction plane. The new microstructure, which completely replaces the previous granular and random structure in the sintered precursor, exhibits dramatically improved transport Jc values at 77 K of ∼17 000 A/cm2 in zero field and ∼4000 A/cm2 at H=1 T (as compared to ∼500 and ∼1 A/cm2, respectively, for the as‐sintered structure), with the severe field dependence of Jc (‘‘weak‐link’’ problem) no longer evident in the new melt‐textured material. The improvement in Jc is attributed to the combined effects of densification, alignment of crystals, and formation of cleaner grain boundaries. Microstructure and distribution of various phases present in the melt‐textured material are discussed in relation to the superconducting properties.
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74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.Mm Grain and twin boundaries

Superconducting oxide films with high transition temperature prepared from metal trifluoroacetate precursors

A. Gupta, R. Jagannathan, E. I. Cooper, E. A. Giess, J. I. Landman, and B. W. Hussey

Appl. Phys. Lett. 52, 2077 (1988); http://dx.doi.org/10.1063/1.99752 (3 pages) | Cited 133 times

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Superconducting thin films of Y‐Ba‐Cu oxide have been prepared on yttria‐stabilized zirconia substrates using metal trifluoroacetate spin‐on precursors. The films exhibit an extremely sharp resistive transition with zero resistance at temperatures as high as 94 K. The superconducting phase is formed by a three‐step process: (a) decomposition of the spun‐on trifluoroacetate film to the fluorides, (b) conversion of the fluorides to oxides by reacting with water vapor, and (c) annealing followed by slow cooling in oxygen. The properties of the films depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c‐axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the film is more randomly oriented and exhibits a broader transition to zero resistance.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

High critical field anisotropy of superconducting Bi‐Sr‐Ca‐Cu oxide from highly oriented thin films

J. H. Kang, R. T. Kampwirth, and K. E. Gray

Appl. Phys. Lett. 52, 2080 (1988); http://dx.doi.org/10.1063/1.99753 (3 pages) | Cited 21 times

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Superconducting films of Bi‐Sr‐Ca‐Cu oxides have been grown on MgO substrates by multitarget magnetron sputtering. After post‐annealing in an oxygen atmosphere, zero resistance was obtained at about 80 K. X‐ray diffraction indicates a high degree of preferential growth of the c axis perpendicular to the substrate. Measurements of the upper critical field Bc2(T) of these films show critical field slopes (B′c2≡−dBc2/dT at Tc) of 8.5 and 0.56 T/K, respectively, for B parallel and perpendicular to the substrate. The anisotropy of ∼15 and the Bc2∥ are the highest values yet reported for high‐temperature superconductors.
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74.25.Op Mixed states, critical fields, and surface sheaths
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
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