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5 Jun 1989

Volume 54, Issue 23, pp. 2287-2377

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Nonlinear optical properties of highly oriented polydiacetylene evaporated films

T. Kanetake, K. Ishikawa, T. Hasegawa, T. Koda, K. Takeda, M. Hasegawa, K. Kubodera, and H. Kobayashi

Appl. Phys. Lett. 54, 2287 (1989); http://dx.doi.org/10.1063/1.101104 (3 pages) | Cited 60 times

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Third‐order harmonic generation has been measured on highly oriented polydiacetylene (PDA) films prepared by the vacuum deposition method. Experimental values of the third‐order electric susceptibility χ(3) measured for pumping laser polarized parallel to the polymer chain show a sharp three‐photon resonance to the 1Bu exciton in PDA. Potential usefulness of these highly oriented PDA evaporated films in nonlinear optical applications is suggested.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Qn Polymers; organic compounds
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Low‐power optical bistability in a thermally stable AlGaAs étalon

Eric Masseboeuf, Olof Sahlén, Ulf Olin, Nils Nordell, Michael Rask, and Gunnar Landgren

Appl. Phys. Lett. 54, 2290 (1989); http://dx.doi.org/10.1063/1.101105 (3 pages) | Cited 7 times

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Optical bistability with 10 mW input power is reported in a thermally stable, nonlinear AlGaAs étalon. A 3‐μm‐thick silver layer, which serves both as high‐reflecting mirror and heat sink, makes it possible to operate the device at arbitrary duty cycles and pulse lengths up to 0.5 s, without any regenerative pulsations, at room temperature. The device operation depends on the plasma‐induced electronic nonlinearity, and switching times are typically 10 ns. Device performance is compared with results from a numerical model which takes diffraction, diffusion, and heat conduction into account.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
42.79.Dj Gratings

Smoothing of multilayer x‐ray mirrors by ion polishing

Eberhard Spiller

Appl. Phys. Lett. 54, 2293 (1989); http://dx.doi.org/10.1063/1.101106 (3 pages) | Cited 40 times

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Ion bombardment at grazing angles of incidence is used to smoothen the boundaries within multilayer x‐ray mirrors. Increases in the reflectivity by a factor of 2 for soft x rays have been obtained for RhRu‐C mirrors with periods of 60 Å.
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42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
81.05.Bx Metals, semimetals, and alloys
78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Focusing of particle beams using two‐stage laser ablation

M. A. Kadar‐Kallen and K. D. Bonin

Appl. Phys. Lett. 54, 2296 (1989); http://dx.doi.org/10.1063/1.101107 (3 pages) | Cited 10 times

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We report a new technique for producing focused beams of neutrals, ions, and clusters using two‐stage laser ablation. We have produced a collimated beam and beams which were focused in one and two dimensions. The on‐axis density is 5×1015 atoms/cm3 for a barium beam focused in two dimensions over a distance of 10.7 cm. For a collimated beam the density is 1015 atoms/cm3 at the same distance.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
79.20.Ds Laser-beam impact phenomena
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
29.27.-a Beams in particle accelerators

76 W cw monolithic laser diode arrays

Masamichi Sakamoto, David F. Welch, John G. Endriz, Donald R. Scifres, and William Streifer

Appl. Phys. Lett. 54, 2299 (1989); http://dx.doi.org/10.1063/1.101366 (2 pages) | Cited 8 times

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cw output power levels of 76 and 55 W have been obtained from 1 cm monolithic AlGaAs laser diode arrays with an aperture width of 3 and 2 mm at a heatsink temperature of 0 and 23 °C, respectively. One of the diodes has been operated for over 5000 h at varying power levels between 5 and 10 W and at varying temperatures between 20 and 40 °C and operated successfully for over 3000 h at power levels over 7 W.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Dual wavelength visible upconversion laser

R. A. McFarlane

Appl. Phys. Lett. 54, 2301 (1989); http://dx.doi.org/10.1063/1.101108 (2 pages) | Cited 44 times

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Laser operation has been obtained at 551 and 671 nm by pumping 5% Er:YLiF4 at 791 nm. Time dependence studies of the emission show that the excitation process has a component related to cooperative energy transfer, and a component related to stepwise multiple photon absorption. Self‐Q‐switched operation at 551 nm is seen to impart a time dependence to an otherwise cw output at 671 nm.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Rz Doped-insulator lasers and other solid state lasers
78.45.+h Stimulated emission
42.60.Fc Modulation, tuning, and mode locking

Electron beam generation by electron multiplication

C. Murray, B. Szapiro, and J. J. Rocca

Appl. Phys. Lett. 54, 2303 (1989); http://dx.doi.org/10.1063/1.101109 (3 pages)

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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.
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41.75.Ht Relativistic electron and positron beams
07.77.-n Atomic, molecular, and charged-particle sources and detectors
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
79.20.Hx Electron impact: secondary emission

Pt/Ti/p‐In0.53Ga0.47As low‐resistance nonalloyed ohmic contact formed by rapid thermal processing

A. Katz, W. C. Dautremont‐Smith, S. N. G. Chu, P. M. Thomas, L. A. Koszi, J. W. Lee, V. G. Riggs, R. L. Brown, S. G. Napholtz, J. L. Zilko, and A. Lahav

Appl. Phys. Lett. 54, 2306 (1989); http://dx.doi.org/10.1063/1.101110 (3 pages) | Cited 29 times

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Very low resistance nonalloyed ohmic contacts of Pt/Ti to 1.5×1019 cm−3 Zn‐doped In0.53Ga0.47As have been formed by rapid thermal processing. These contacts were ohmic as deposited with a specific contact resistance value of 3.0×10−4 Ω cm2. Cross‐sectional transmission electron microscopy showed a very limited interfacial reacted layer (20 nm thick) between the Ti and the InGaAs as a result of heating at 450 °C for 30 s. The interfacial layer contained mostly InAs and a small portion of other five binary phases. Heating at 500 °C or higher temperatures resulted in an extensive interaction and degradation of the contact. The contact formed at 450 °C, 30 s exhibited tensile stress of 5.6×109 dyne cm−2 at the Ti/Pt bilayer, but the metal adhesion remained strong. Rapid thermal processing at 450 °C for 30 s decreased the specific contact resistance to a minimum with an extremely low value of 3.4×10−8 Ω cm2 (0.08 Ω mm), which is very close to the theoretical prediction.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.35.Dv Composition, segregation; defects and impurities
81.40.Rs Electrical and magnetic properties related to treatment conditions

Synthesis and properties of ultrafine AlN powder by rf plasma

Kazuhiro Baba, Nobuaki Shohata, and Masatomo Yonezawa

Appl. Phys. Lett. 54, 2309 (1989); http://dx.doi.org/10.1063/1.101111 (3 pages) | Cited 29 times

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High‐purity ultrafine AlN powder was synthesized by rf plasma through direct nitridation of Al. The specific surface area was about 30 m2 /g under typical experimental conditions. Ultrafine AlN powder showed excellent sinterability, compared with conventional AlN powders, whose particle sizes were more than 0.5 μm. The thermal conductivity for the sintered body reached 220 W/m K when sintered at 1900 °C, and 110 W/m K when sintered at 1400 °C, by using YF3 as a sintering aid.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
52.50.-b Plasma production and heating

Generation of strong composition‐modulated structures and absence of ordered structures in InGaP crystals grown on (110) GaAs substrates by metalorganic chemical vapor deposition

O. Ueda, M. Takechi, and J. Komeno

Appl. Phys. Lett. 54, 2312 (1989); http://dx.doi.org/10.1063/1.101112 (3 pages) | Cited 13 times

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InGaP crystals grown on (110) GaAs substrates by chemical vapor deposition have been structurally investigated by transmission electron microscopy. No superstructure spots are present in electron diffraction patterns from (110) plan view and (110) and (001) cross sections. However, composition‐modulated structures with strong amplitude are found not only in the 〈001〉 but in the 〈110〉 directions. They are found to be stable in the form of columnar domains during crystal growth. These results strongly suggest that atomic ordering and spinodal decomposition of the crystal are competing on the growth surface via surface diffusion of deposited atoms.
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68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Real‐space transfer from quantum wells by polar optical phonon scattering

Craig S. Lent, Lie Liang, and Wolfgang Porod

Appl. Phys. Lett. 54, 2315 (1989); http://dx.doi.org/10.1063/1.101113 (3 pages) | Cited 9 times

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We calculate the rate at which electrons bound in a semiconductor quantum well are scattered out of the well by absorption or emission of polar optical phonons. This escape rate is important in real‐space transfer devices and as a loss mechanism in high electron mobility transistors. Both quantum confinement effects and the two‐dimensional (2D) to three‐dimensional (3D) nature of the scattering are included. For all but very shallow wells, the real‐space transfer rate is much smaller than either the bulk (3D) scattering rate or the confined (2D) scattering rate. Quantum resonances in the final state result in oscillations in the scattering rate as a function of electron energy.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.50.Bk General theory, scattering mechanisms

Fabrication and characterization of lateral InP/InGaAsP heterojunctions and bipolar transistors

H‐J. Yoo, J. R. Hayes, C. Caneau, R. Bhat, and M. Koza

Appl. Phys. Lett. 54, 2318 (1989); http://dx.doi.org/10.1063/1.101114 (3 pages) | Cited 2 times

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We have investigated the fabrication of lateral InP/InGaAsP heterojunctions using both wet chemical and in situ melt‐back etching and regrowth to form the device junctions. The current/voltage characteristics of the melt‐back‐etched and regrown heterojunctions exhibit ideality factors as low as 1.25. In addition, we have fabricated lateral heterojunction bipolar transistors with 2 μm base widths which exhibit a current gain of 6. These results indicate that regrown heterojunctions have adequate injection efficiency to form the active region of devices.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
68.35.Fx Diffusion; interface formation
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Study of oxygen addition to CF3Br reactive ion etching plasmas: Effects on silicon surface chemistry and etching behavior

T. D. Bestwick, G. S. Oehrlein, D. Angell, P. L. Jones, and J. W. Corbett

Appl. Phys. Lett. 54, 2321 (1989); http://dx.doi.org/10.1063/1.101115 (3 pages) | Cited 1 time

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The etching of silicon in CF3Br/O2 plasmas has been examined. In situ x‐ray photoelectron spectroscopy shows that silicon surfaces etched in CF3Br/O2 plasmas with a proportion of 30% O2 or less are covered with a reaction layer that is mainly due to bromine bonded to silicon. As the proportion of oxygen is increased above 30% the reaction layer becomes thicker and contains mainly fluorine and oxygen, and the silicon etch rate decreases simultaneously.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Self‐deformed and hysteretic photocurrent spectra of quantum wells with a load resistor

Yasunori Tokuda, Kyozo Kanamoto, and Noriaki Tsukada

Appl. Phys. Lett. 54, 2324 (1989); http://dx.doi.org/10.1063/1.101116 (3 pages) | Cited 8 times

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We report a study of the self‐deformation of the photocurrent spectra of a quantum well p‐i‐n structure connecting with a high series resistor. The observed phenomena are interpreted in terms of the modulation of the internal electric field at the intrinsic quantum well region by the photocurrent itself. Furthermore, it is predicted and demonstrated that bistability of the photocurrent is achieved as a function of the wavelength.
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73.50.Pz Photoconduction and photovoltaic effects
71.35.-y Excitons and related phenomena
85.30.De Semiconductor-device characterization, design, and modeling
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Desorption of triethylgallium during metalorganic molecular beam epitaxial growth of GaAs

M. Uneta, Y. Watanabe, and Y. Ohmachi

Appl. Phys. Lett. 54, 2327 (1989); http://dx.doi.org/10.1063/1.101117 (3 pages) | Cited 6 times

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The desorption of triethylgallium (TEGa) adsorbed on As‐ and Ga‐terminated surfaces during metalorganic molecular beam epitaxial (MOMBE) growth of GaAs is investigated by measuring the As flux dependence of the growth rate. The growth rate decreases with decreasing As flux in the substrate temperature range where the desorption of triethylgallium adsorbed on the growth surface occurs. This indicates that adsorbed TEGa (adTEGa) molecules desorb more rapidly on the Ga‐terminated surface than on the As‐terminated surface. To investigate the adTEGa desorptions on As‐ and Ga‐terminated surfaces independently, the growth rates in alternating TEGa‐As4 supply mode are compared with those in simultaneous supply mode. The growth rates in the alternating supply mode become smaller than those in the simultaneous supply mode as the substrate temperature is raised above 500 °C. This result demonstrates that the adTEGa desorption rate on the Ga‐terminated surface is larger than that on the As‐terminated surface.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Band‐gap profiling for improving the efficiency of amorphous silicon alloy solar cells

S. Guha, J. Yang, A. Pawlikiewicz, T. Glatfelter, R. Ross, and S. R. Ovshinsky

Appl. Phys. Lett. 54, 2330 (1989); http://dx.doi.org/10.1063/1.101118 (3 pages) | Cited 55 times

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We have developed an amorphous silicon alloy based solar cell with a novel structure in which the optical gap of the intrinsic layer changes in a substantial portion of the bulk. Computer simulation studies show that for a given short circuit current, it is possible with this structure to obtain higher open circuit voltage and fill factor than in a conventional cell design. Experimental cell structures have been made and confirm the theoretical prediction. The new cell design shows a considerable improvement in efficiency. Incorporation of this structure in the bottom cell of a triple device has resulted in the achievement of 13.7% efficiency under global AM1.5 illumination.
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84.60.Jt Photoelectric conversion
73.50.Pz Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.66.-w Optical properties of specific thin films

Near‐ideal lateral scaling in abrupt Al0.48In0.52As/In0.53Ga0.47As heterostructure bipolar transistors prepared by molecular beam epitaxy

B. Jalali, R. N. Nottenburg, Y. K. Chen, A. F. J. Levi, D. Sivco, A. Y. Cho, and D. A. Humphrey

Appl. Phys. Lett. 54, 2333 (1989); http://dx.doi.org/10.1063/1.101119 (3 pages) | Cited 24 times

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We demonstrate near‐ideal lateral scaling in abrupt junction Al0.48In0.52As /In0.53Ga0.47As heterostructure bipolar transistors. Current gain β=162 and 122 has been realized in transistors with emitter stripe width of 50 and 0.6 μm, respectively. The excellent lateral scaling occurs because the 0.5 eV emitter injection energy results in nonequilibrium vertical electron transport in the thin (700 Å) InGaAs base.
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85.30.Pq Bipolar transistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
73.61.Ey III-V semiconductors

Iron‐doped semi‐insulating InP grown by chemical beam epitaxy

W. T. Tsang, A. S. Sudbo, L. Yang, R. Camarda, and R. E. Leibenguth

Appl. Phys. Lett. 54, 2336 (1989); http://dx.doi.org/10.1063/1.101120 (3 pages) | Cited 10 times

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We have prepared Fe‐doped InP epilayers by chemical beam epitaxy using a thermal atomic Fe beam. Epilayers having high resistivities (≳107 Ω cm) were obtained over a wide range of Fe concentrations. Resistivities as high as 1.3×108 Ω cm have been obtained. Such resistivity is almost equal to the theoretical value of 1.37×108 Ω cm that we estimate for intrinsic InP. The current‐voltage characteristics exhibit both an ohmic and a space‐charge‐limited regime, and are consistent with the theory of single‐carrier injection into a trap‐free insulator. Pinning of the Fermi level near midgap by Fe‐related deep levels is the mechanism by which the epilayer is made highly resistive. At room temperature, these traps are apparently deep enough that the carrier emission rate is negligible.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors

Interface‐trap transformation at radiation‐damaged (111)Si/SiO2 interface

Yu Wang, T. P. Ma, and R. C. Barker

Appl. Phys. Lett. 54, 2339 (1989); http://dx.doi.org/10.1063/1.101522 (3 pages) | Cited 6 times

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This letter presents the results of our recent study on the post‐irradiation behavior of the interface trap distribution in metal‐SiO2‐Si capacitors made on Si substrates of (111) orientation. It will be shown that the interface trap distribution in these (111) samples measured immediately after x‐ray irradiation is qualitatively similar to what was observed in the (100) counterpart: a prominent peak appears in the upper half of the Si band gap (Ev+0.75 eV). Subsequent time‐dependent evolution behavior of this peak, however, is distinctly different for samples with the two different orientations. While in (100) samples a second peak in the lower half of the band gap would develop over time, resulting in a double‐peak interface trap distribution [see, for example, E. F. da Silva, Y. Nishioka, and T.‐P. Ma, Appl. Phys. Lett. 51, 270 (1987)], the most salient feature observed in (111) samples is the gradual shift of the peak position with time toward the lower half of the Si band gap, and eventually a single peak will reside below midgap. The movement of this peak has been found to be thermally accelerated, with an apparent activation energy of about 0.4±0.1 eV. It has also been found that the gate‐induced compressive strain at the Si/SiO2 interface plays an important role in the peak movement. In addition, the presence of a gate bias and its polarity also significantly affect the post‐irradiation behavior of the interface trap distribution. The results may be explained in terms of the atomic relaxation of the bonding defect at the (111)Si/SiO2 interface.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
61.72.Bb Theories and models of crystal defects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Ion beam induced epitaxy of deposited amorphous Si and Si‐Ge films

A. J. Yu, J. W. Mayer, D. J. Eaglesham, and J. M. Poate

Appl. Phys. Lett. 54, 2342 (1989); http://dx.doi.org/10.1063/1.101523 (3 pages) | Cited 16 times

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The epitaxial recrystallization of amorphous electron beam deposited silicon and silicon‐germanium layers on 〈100〉 silicon substrates was induced by a 2.5 MeV Ar beam irradiation in the temperature range of 200–400 °C. Even in films with bulk oxygen concentration of 0.5 at. %, layer‐by‐layer regrowth was observed with an order of magnitude reduction in growth rate when compared to clean, implanted amorphous silicon. Irradiation of codeposited Si‐Ge amorphous layers results in the layer‐by‐layer regrowth of a Si88Ge12 alloy. Ion beam assisted epitaxy of Si and Si‐Ge was found to be sensitive to interfacial cleanliness, but layer‐by‐layer regrowth was observed for samples that did not demonstrate regrowth under conventional furnace annealing.
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81.15.Np Solid phase epitaxy; growth from solid phases
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

In‐plane hole effective masses in InxGa1−xAs/Al0.15Ga0.85As modulation‐doped heterostructures

M. Jaffe, J. E. Oh, J. Pamulapati, J. Singh, and P. Bhattacharya

Appl. Phys. Lett. 54, 2345 (1989); http://dx.doi.org/10.1063/1.101121 (2 pages) | Cited 14 times

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We have determined the strain dependence of the in‐plane hole effective mass in pseudomorphic Inx Ga1−x As/Al0.15 Ga0.85As modulation‐doped heterostructures by low‐temperature Shubnikov–de Haas measurements. An effective mass equal to 0.18m0 is measured for x=0.2. The measured values are in good agreement with theoretical calculations.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.At Surface states, band structure, electron density of states

Control of Al/GaAs Schottky barrier height by high Ce doping

Kazuyuki Hirose and Ethan Foxman

Appl. Phys. Lett. 54, 2347 (1989); http://dx.doi.org/10.1063/1.101122 (2 pages) | Cited 2 times

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Al/GaAs Schottky barrier contacts are fabricated with different Ce doping concentrations in the last 100 Å of GaAs before the metal/GaAs interface. Both n‐ and p‐type Schottky barrier heights (SBHs) are measured by current‐voltage and capacitance‐voltage methods. The n‐type SBH is found to decrease with the increasing Ce doping concentration, and the p‐type SBH is found to increase to a lesser degree. These SBH changes are considered to be due to energy gap narrowing at the GaAs surface caused by high Ce doping.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.20.At Surface states, band structure, electron density of states

Microstructure of epitaxial ErBa2Cu3O7−x thin films grown on MgO (100) substrates by rf magnetron sputtering

J. Chang, M. Nakajima, K. Yamamoto, and A. Sayama

Appl. Phys. Lett. 54, 2349 (1989); http://dx.doi.org/10.1063/1.101524 (3 pages) | Cited 6 times

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The microstructural properties of superconducting ErBa2Cu3O7−x films on single‐crystal MgO substrates are studied by transmission electron microscopy. The as‐grown films are single‐crystal‐like and are composed of subgrains of 0.1–0.2 μm in size. Due to annealing, the dislocations at the subgrain boundaries disappeared. The annealed films are epitaxial with either the a or the b axis of the ErBa2Cu3O7−x unit cell along 〈100〉 directions of the MgO substrate. The stress caused by lattice mismatch is relaxed by the formation of misfit dislocations at the film/substrate interface.
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68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Cd Deposition by sputtering

High current density in bulk YBa2Cu3Ox superconductor

K. Salama, V. Selvamanickam, L. Gao, and K. Sun

Appl. Phys. Lett. 54, 2352 (1989); http://dx.doi.org/10.1063/1.101525 (3 pages) | Cited 349 times

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A liquid phase processing method for the fabrication of bulk YBa2Cu3Ox superconductors with large current carrying capacity has been developed. Slow cooling through the peritectic transformation (1030–980 °C) has been shown to control the microstructure of these superconductors. A cooling rate of 1 °C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area. Current density up to 18 500 A/cm2 has been obtained by continuous direct current measurements and in excess of 62 000 A/cm2 with pulse current of 10 ms duration and 75 000 A/cm2 using 1 ms pulse. The strong magnetic field dependence observed in sintered bulk 1‐2‐3 superconductors is also minimized to a large extent where a current density in excess of 37 000 A/cm2 is obtained in a field of 6000 G.
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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
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.Mm Grain and twin boundaries

Microwave noise emission from high Tc thin films

G. Jung, J. Konopka, P. Gierłowski, and W. Kula

Appl. Phys. Lett. 54, 2355 (1989); http://dx.doi.org/10.1063/1.101526 (3 pages) | Cited 6 times

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A pronounced X‐band microwave noise emission from Y‐Ba‐Cu‐O thin films has been observed. Emission depends strongly on temperture, bias current, and magnetic field. Two types of emission lines can be distinguished in the power versus dc bias spectra. The lines which remain at stable current positions against temperature we tentatively ascribe to the interaction of depinned flux flow with a two‐dimensional Josephson junction array. The lines that appear at fixed voltage positions may be attributed to the Josephson radiation of a distributed network of junctions. No significant emission was detected from Bi‐Ca‐Sr‐Cu‐O films.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.40.-n Fluctuation phenomena
74.50.+r Tunneling phenomena; Josephson effects
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