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8 Aug 1988

Volume 53, Issue 6, pp. 457-537

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High‐power phase‐locked InGaAs strained‐layer quantum well heterostructure periodic laser array

J. N. Baillargeon, P. K. York, C. A. Zmudzinski, G. E. Fernández, K. J. Beernink, and J. J. Coleman

Appl. Phys. Lett. 53, 457 (1988); http://dx.doi.org/10.1063/1.99883 (3 pages) | Cited 18 times

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Data are presented on high‐power strained‐layer InGaAs quantum well heterostructure laser arrays. These devices are periodic nonplanar arrays, formed by a single metalorganic chemical vapor deposition growth over a selectively etched corrugated GaAs substrate. The corrugation serves to provide both stripe definition and index guiding while suppressing lateral lasing perpendicular to the stripes. Maximum pulsed optical powers of 2.5 W/facet (width=1600 μm, length=440 μm) for an emission wavelength of 1.03 μm have been obtained from uncoated devices having threshold current densities in the range 290–600 A/cm2. Far‐field radiation patterns indicate that the arrays are phase locked.
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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
42.60.By Design of specific laser systems

All‐optical bistability in nematic liquid crystals at 20 μW power levels

A. D. Lloyd and B. S. Wherrett

Appl. Phys. Lett. 53, 460 (1988); http://dx.doi.org/10.1063/1.99884 (2 pages) | Cited 8 times

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Optical switches at power levels as low as 14 μW, allowing bistable operation with compact disk laser systems, are reported in optimized cavities containing planar‐aligned nematic liquid crystals.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
07.60.-j Optical instruments and equipment
42.79.-e Optical elements, devices, and systems

Highly collimated laser beams from grating coupled emission Pb1−xSnxSe/Pb1−x−yEuySnxSe diode lasers

Y. Shani, A. Katzir, M. Tacke, and H. M. Preier

Appl. Phys. Lett. 53, 462 (1988); http://dx.doi.org/10.1063/1.100399 (2 pages)

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Grating coupled emission Pb1−xSnxSe/Pb1−x−yEuySnxSe double‐heterostructure stripe‐geometry diode lasers were fabricated using molecular beam epitaxy. Low‐divergence far‐field patterns of ∼5° for multimode operation and ∼2° for single‐mode operation were obtained. These are the lowest values ever achieved with Pb salt lasers.
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42.60.By Design of specific laser systems
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

High‐power, diffraction‐limited‐beam operation from phase‐locked diode‐laser arrays of closely spaced ‘‘leaky’’ waveguides (antiguides)

D. Botez, L. Mawst, P. Hayashida, G. Peterson, and T. J. Roth

Appl. Phys. Lett. 53, 464 (1988); http://dx.doi.org/10.1063/1.99885 (3 pages) | Cited 28 times

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A novel type of phase‐locked diode‐laser array is demonstrated: an array of closely spaced index depressions (antiguides). The arrays are ten‐element AlGaAs/GaAs devices fabricated by metalorganic chemical vapor deposition and liquid phase epitaxy over a patterned substrate. The fundamental and highest‐order modes of the array of antiguides have negligible radiation loss: 20–30 times less than that for a single antiguide. The modal‐gain differentials between adjacent array modes are at least an order of magnitude larger than those for evanescently coupled arrays of positive‐index guides. Fundamental‐array‐mode operation in a virtually diffraction‐limited‐beam (1.4°) pattern is obtained to 200 mW. Out‐of‐phase‐mode operation in a virtually diffraction‐limited‐beam (1.2°) pattern is achieved to 110 mW/uncoated facet. The inherent array‐mode stability of antiguided arrays is discussed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Gn Optical waveguides and couplers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Nonlinear mixing and phase conjugation in broad‐area diode lasers

M. Lucente, G. M. Carter, and J. G. Fujimoto

Appl. Phys. Lett. 53, 467 (1988); http://dx.doi.org/10.1063/1.99871 (3 pages) | Cited 5 times

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Four‐wave mixing is investigated in broad‐area diode lasers. Two external fields are injected into the device using a phase conjugation geometry and the nonlinear four‐wave mixing signal observed by performing spectrally resolved measurement of the far field. By varying the injection geometry, the excited mode of the broad‐area diode can be controlled. The gain nonlinearity generates a conjugate wave within the device, thereby resulting in far‐field emission in the conjugate direction. Nonlinear conjugate signal efficiency levels of ∼−21 dB have been observed.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.55.Px Semiconductor lasers; laser diodes

Influence of the applied field frequency (27–2450 MHz) in high‐frequency sustained plasmas used to etch polyimide

G. Sauvé, M. Moisan, J. Paraszczak, and J. Heidenreich

Appl. Phys. Lett. 53, 470 (1988); http://dx.doi.org/10.1063/1.99872 (3 pages) | Cited 8 times

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The effect of the plasma stimulating frequency upon the etching of polyimide is reported. For the first time, a system has been developed which generates, over a large frequency domain (27–2450 MHz), a high‐frequency (HF) produced plasma by identical means (surface wave propagation) in a fixed plasma volume. It is found that the addition of CF4 to an O2 plasma affects the etch rate of polyimide in a manner which depends upon the operating frequency of the HF plasma. In particular, a maximum of etch rate per watt is observed around 50 MHz.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
52.80.Pi High-frequency and RF discharges

Variable‐energy positron‐beam studies of SiO2/Si irradiated by ionizing radiation

A. Uedono, S. Tanigawa, K. Suzuki, and K. Watanabe

Appl. Phys. Lett. 53, 473 (1988); http://dx.doi.org/10.1063/1.100616 (3 pages) | Cited 16 times

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Variable‐energy positron‐beam studies have been carried out on Si with a 1.61 μm overlayer of SiO2 irradiated by x ray and γ ray up to the dose of 5×105 R. The Doppler broadening of annihilation photons was found to be strongly influenced by x‐ray irradiation, and the effect was extended homogeneously over the entire oxide layer. A trapping model which neglects positron diffusion effects was applied to the dependence of the line shape parameter S on incident positron energy.
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78.70.Bj Positron annihilation
61.80.-x Physical radiation effects, radiation damage
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Photoluminescence and magnetoreflectivity study of Zn1−xFexSe epilayers

X. Liu, A. Petrou, B. T. Jonker, G. A. Prinz, J. J. Krebs, and J. Warnock

Appl. Phys. Lett. 53, 476 (1988); http://dx.doi.org/10.1063/1.99873 (3 pages) | Cited 12 times

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Single‐crystal films of (001)Zn1−xFexSe (x=0.017, 0.027, 0.043) grown by molecular beam epitaxy on (001)GaAs have been studied using reflectivity and photoluminescence spectroscopies. Data have been obtained over the temperature range 4–77 K in magnetic fields up to 8 T in the spectral region near the band gap of 2.8 eV. The luminescence spectra show the two lowest interband excitonic transitions. From these spectra, the Zeeman splitting of the bands and the corresponding Fe2+‐band electron exchange integrals were determined. The temperature dependence of the band splitting was determined through reflectivity measurements. These studies confirm the fact that Zn1−xFexSe exhibits Van Vleck paramagnetism and yield the spin‐orbit splitting of the lowest Fe2+ crystal field states.
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78.55.Hx Other solid inorganic materials
78.66.-w Optical properties of specific thin films
75.50.Pp Magnetic semiconductors
75.20.Ck Nonmetals

Two‐dimensional electron gas at a Ga0.47In0.53As/ (AlxGa1−x)0.48In0.52As interface

S. Ben Amor, L. Dmowski, J. C. Portal, J. P. Praseuth, and L. Goldstein

Appl. Phys. Lett. 53, 479 (1988); http://dx.doi.org/10.1063/1.99874 (3 pages) | Cited 3 times

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We report the first observation of a two‐dimensional electron gas in (AlGa) InAs/GaInAs heterostructures. Angular‐dependent Shubnikov–de Haas oscillations and quantum Hall effect prove the two dimensionality of the system. We discuss the effect of the barrier composition on the electronic structure of the system. A significant number of electrons remain confined even for the smallest confinement barrier. Persistent photoconductivity was observed at low temperature.
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73.40.Kp III-V 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
73.50.Pz Photoconduction and photovoltaic effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Neutral E′ centers in microwave downstream plasma‐enhanced chemical‐vapor‐deposited silicon dioxide

W. L. Warren, P. M. Lenahan, B. Robinson, and J. H. Stathis

Appl. Phys. Lett. 53, 482 (1988); http://dx.doi.org/10.1063/1.100617 (3 pages) | Cited 29 times

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We have utilized electron spin resonance and capacitance versus voltage measurements to study E′ centers generated by the photoemission of electrons into silicon dioxide films prepared by plasma‐enhanced chemical vapor deposition (PECVD). The oxides were deposited on crystalline silicon substrates downstream from a microwave discharge. The E′ center is an unpaired electron in a nonbonding sp3 hybrid orbital on a silicon bonded to three oxygen atoms. In conventional thermal SiO2 films on silicon, E′ centers are the dominant deep hole traps. However, the E′ centers generated in the PECVD oxides are generated by electron injection into the oxide and are almost certainly electrically neutral. Our results unequivocally demonstrate fundamental differences in the point defects in thermally grown SiO2 on silicon and PECVD oxides.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Simulation of extrinsic bistability of resonant tunneling structures

H. C. Liu

Appl. Phys. Lett. 53, 485 (1988); http://dx.doi.org/10.1063/1.99875 (2 pages) | Cited 32 times

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A simple biasing circuit for measuring current‐voltage characteristics of resonant tunneling double‐barrier structures exhibits extrinsic bistabilities due to oscillations, which we show through large‐signal simulations.
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73.40.Gk Tunneling
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
72.20.-i Conductivity phenomena in semiconductors and insulators

Observation of pn junctions on implanted silicon using a scanning tunneling microscope

Sumio Hosaka, Shigeyuki Hosoki, Keiji Takata, Katsutada Horiuchi, and Nobuyoshi Natsuaki

Appl. Phys. Lett. 53, 487 (1988); http://dx.doi.org/10.1063/1.99876 (3 pages) | Cited 44 times

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Si pn junctions fabricated by photoresist masked As+ implantation were observed using current imaging tunneling spectroscopy (CITS) in a scanning tunneling microscope (STM). Using the CITS, a specific bias was chosen to define n‐type or p‐type areas according to whether or not current flowed. The pn junctions could be easily identified from the current image at this bias and in the STM topographic image. It also proved possible to find processing faults related to implantation. The STM images also identified the structure (corrugations) near the junctions, associated with volume expansion caused by implantation and annealing.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
73.25.+i Surface conductivity and carrier phenomena
68.35.B- Structure of clean surfaces (and surface reconstruction)

Hot‐electron transport in a graded band‐gap base heterojunction bipolar transistor

J. R. Hayes and J. P. Harbison

Appl. Phys. Lett. 53, 490 (1988); http://dx.doi.org/10.1063/1.99877 (3 pages) | Cited 1 time

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In this letter we report the direct observation of electron heating in an electric field using hot‐electron spectroscopy. The device structure used for the study was a graded band‐gap base heterojunction bipolar transistor, fabricated in the GaAs/AlGaAs semiconductor alloy system. A thermal electron distribution at 4.2 K was injected from the emitter into the base of a transistor that was compositionally graded to yield a quasielectric field of 20 kV cm−1 . The equilibrium electron distribution was heated by the electric field and could be characterized at the end of the 900 Å base region by an effective electron temperature of 650 K.
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85.30.Pq Bipolar transistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors

Al0.3Ga0.7As/GaAs metal‐insulator‐semiconductor‐type field‐effect transistor fabricated on an InP substrate

S. Agarwala, M. B. Patil, C. K. Peng, and H. Morkoç

Appl. Phys. Lett. 53, 493 (1988); http://dx.doi.org/10.1063/1.99878 (2 pages) | Cited 7 times

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A metal‐insulator‐semiconductor‐type Al0.3Ga0.7As/GaAs field‐effect transistor with 1‐μm‐long by 145‐μm‐wide gates and intrinsic transconductance of 180 mS/mm has been demonstrated on an InP substrate. The dislocation propagation is minimized by incorporating a superlattice on InP, and a 1.5 μm undoped GaAs buffer layer is grown prior to the actual channel to ensure good quality of the 250 Å active layer. A channel mobility of 1920 cm2/(V s) and a carrier concentration of 1.28×1018 cm−3 have been measured at 300 K. The device exhibits excellent pinch‐off, and the gate‐to‐source reverse breakdown voltage is greater than 5 V. The low output conductance of 2.5 mS/mm indicated small parallel conduction in the undoped GaAs buffer layer. Also, very little hysteresis was found in the current‐voltage characteristics, implying few traps in the epilayer.
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85.30.Tv Field effect devices
73.61.Ey III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Noninteger InAs monolayer well InAs/GaAs single quantum well structures grown by metalorganic chemical vapor deposition

K. Taira, H. Kawai, I. Hase, K. Kaneko, and N. Watanabe

Appl. Phys. Lett. 53, 495 (1988); http://dx.doi.org/10.1063/1.99879 (2 pages) | Cited 24 times

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InAs/GaAs single quantum well structures have been grown by metalorganic chemical vapor deposition. The grown wells are 1.03, 1.3, and 1.7 InAs monolayers thick. The 4 K photoluminescence spectra exhibit strong and narrow peaks, their energy decreasing smoothly with increasing well thickness. The noninteger value is interpreted on the model that the interface is macroscopically flat but has valleys and hills with their lateral extent smaller than excitons. The effective interface position is determined by their relative lateral extent.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Reverse dopant redistribution during the initial stages of the oxidation of heavily doped silicon in dry oxygen

Hisham Z. Massoud

Appl. Phys. Lett. 53, 497 (1988); http://dx.doi.org/10.1063/1.100618 (3 pages) | Cited 3 times

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The oxidation of heavily phosphorus‐doped (100) and (111) silicon in the 800–1000 °C range in dry oxygen was studied in the thin‐film regime using in situ ellipsometry. The oxide growth kinetics indicate that, in the initial stages of oxidation, phosphorus piles up at the Si‐SiO2 interface, resulting in a decrease in the surface concentration of electrically active phosphorus and an oxidation rate similar to that of lightly doped silicon. As the oxide grows, the surface concentration of electrically active phosphorus reaches and exceeds its bulk value, and the SiO2 growth rate gradually becomes similar to that of heavily doped silicon in the thick‐film regime. An empirical model is introduced to account for the influence of this reverse dopant redistribution on SiO2 growth kinetics in the thin‐film regime.
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68.35.Dv Composition, segregation; defects and impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.65.-b Surface treatments
68.35.Fx Diffusion; interface formation

Theoretical approach to the electronic states and core exciton of superlattice ZnSe/GaAs

Dingli Shen, Kaiming Zhang, and Rouli Fu

Appl. Phys. Lett. 53, 500 (1988); http://dx.doi.org/10.1063/1.99880 (3 pages) | Cited 10 times

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The energy‐band structures of superlattice ZnSe/GaAs(001) are calculated using the semiempirical tight binding method. The fundamental gap and effective mass are studied with the variation of layer thickenss. The appearance of core excitons related to impurities B, Al, and Ga is found to be possible in (ZnSe)5/(GaAs)5, qualitatively consistent with a Ga‐bound exciton peak observed in a corresponding heterojunction experiment. It is proposed that interface states would exist at the conduction‐band edge of this material.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Enhancement in activation efficiency for a SiF3‐implanted GaAs layer by a new annealing method

Akiyoshi Tamura, Kaoru Inoue, and Takeshi Onuma

Appl. Phys. Lett. 53, 503 (1988); http://dx.doi.org/10.1063/1.100619 (2 pages)

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We have found a new phenomenon in which the activation efficiency of a SiF3 ‐implanted GaAs layer is increased by the preimplant thermal treatment of the semi‐insulating GaAs substrate with SiO2 encapsulant.
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61.72.Bb Theories and models of crystal defects
61.72.U- Doping and impurity implantation
85.30.Tv Field effect devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Interfacial defect creation by interstitial lithium doping of amorphous hydrogenated silicon

K. Winer and R. A. Street

Appl. Phys. Lett. 53, 505 (1988); http://dx.doi.org/10.1063/1.99881 (3 pages) | Cited 3 times

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We study interstitial doping in amorphous hydrogenated silicon (a‐Si:H) by indiffusion of lithium at 230 °C using secondary ion mass spectrometry, photothermal deflection spectroscopy (PDS), and electron spin resonance. Lithium is distributed nonuniformly in the films with peak concentrations within 300 nm of either interface. Lithium doping introduces up to 1018 paramagnetic defects per cc in a‐Si:H (g=2.0061, ΔHp.p. =5.2 G), equal to the concentration of deep defects created as measured by PDS. The nature of these defects is discussed.
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68.35.Dv Composition, segregation; defects and impurities
68.35.Fx Diffusion; interface formation
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Passivation of paramagnetic Si‐SiO2 interface states with molecular hydrogen

K. L. Brower

Appl. Phys. Lett. 53, 508 (1988); http://dx.doi.org/10.1063/1.100620 (3 pages) | Cited 35 times

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Dry thermal oxides were grown on (111) silicon substrates at 850 °C. The Pb centers associated with this (111) Si‐SiO2 interface were observed with electron paramagnetic resonance to be stable under subsequent annealing in vacuum up to at least 850 °C. The rate of passivation of Pb centers with H2 was observed to be proportional to the concentration of H2 in the oxide and the density of Pb centers. The forward reaction rate constant kf is temperature dependent and obeys the Arrhenius relationship having an activation energy Ef of 1.66±0.06 eV and a pre‐exponential factor k0f of 1.94 (+2./−1.)×10−6 cm3 /s for temperatures at least between 230 and 260 °C. The linear H2 pressure dependence in the rate of passivation and the magnitude of k0f are reasonably consistent with a model in which the H2 molecule reacts directly with Pb centers during its diffusional motion among the interstices of the SiO2 network and the reaction site at Pb centers.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
76.30.Mi Color centers and other defects
81.65.-b Surface treatments
73.40.Ty Semiconductor-insulator-semiconductor structures

Dose effects during solid phase epitaxial regrowth of boron‐implanted, germanium‐amorphized silicon induced by rapid thermal annealing

W. O. Adekoya, M. Hage‐Ali, J. C. Muller, and P. Siffert

Appl. Phys. Lett. 53, 511 (1988); http://dx.doi.org/10.1063/1.99882 (3 pages) | Cited 2 times

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The effect of implanted boron concentration on the solid phase epitaxial regrowth (SPER) kinetics during rapid thermal annealing (RTA) of 73Ge+‐amorphized 〈100〉 silicon in the temperature range 500–575 °C has been studied using Rutherford backscattering and channeling measurements. Relatively flat 11B+ profiles at 5×1019, 1020, and 3×1020 cm−3 were implanted up to a depth ≂0.18 μm into different 73Ge+‐preamorphized 75‐cm‐diam wafers. Following a RTA anneal at 800 °C/10 s (in order to recrystallize the amorphized layer and activate the implanted boron), the wafers were reamorphized with 73Ge+ ions (constant concentration ≂3×1020 cm−3 up to a depth ≂0.2 μm) and the SPER kinetics studied as indicated above. This procedure ensured that the defect densities in the wafers were the same in spite of their different boron doses. Our results clearly show an activation energy reduction from 2.86 eV at 5×1019 atoms/cm3 to 2.6 eV at 3×1020 cm−3 (in spite of the constant defect concentration in the wafers), with a linear relation between the growth rate and the implanted dose throughout the temperature range of study.
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81.15.Np Solid phase epitaxy; growth from solid phases
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth of superconducting V3Si on Si by molecular beam epitaxial techniques

E. T. Croke, R. J. Hauenstein, and T. C. McGill

Appl. Phys. Lett. 53, 514 (1988); http://dx.doi.org/10.1063/1.100621 (3 pages) | Cited 2 times

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Superconducting thin films (500–1000 Å in thickness) of A15 V3Si have been grown on (111)Si substrates through molecular beam epitaxial techniques. V and Si are codeposited in a feedback‐stabilized, 3:1 flux ratio from dual e‐beam evaporators onto clean, heated Si substrates in an ultrahigh vacuum chamber. For the first time, the superconducting A15 V3Si phase is metastably fabricated directly on a crystalline Si substrate without the formation of thermodynamically favored Si‐rich VxSiy phases. Our films exhibit superconductivity only within a narrow range of intermediate growth temperatures (centered near 400 °C), with an optimum Tc of 12.5 K. X‐ray diffraction shows the superconducting films to be polycrystalline A15 V3Si. For slightly higher growth temperatures (≊530 °C), Auger profile, x‐ray, and transmission electron microscopy measurements indicate the appearance of an intermediate layer of roughly 1:1 V:Si composition. Our observations demonstrate that a growth temperature near 400 °C results in successful nucleation of the superconducting A15 phase while minimizing solid phase reaction with the substrate during V3Si growth.
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74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Smooth high Tc Y1Ba2Cu3Ox films by laser deposition at 650 °C

C. C. Chang, X. D. Wu, A. Inam, D. M. Hwang, T. Venkatesan, P. Barboux, and J. M. Tarascon

Appl. Phys. Lett. 53, 517 (1988); http://dx.doi.org/10.1063/1.100622 (3 pages) | Cited 42 times

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Superconducting Y1Ba2Cu3Ox films 300 nm thick with local surface roughness <5 nm have been prepared by laser deposition at 650 °C and subsequent heat treatments at 450 °C; highest zero resistance temperature was above 85 K. Smooth topography and low‐temperature processing are crucial for device fabrication. These films are crack‐free and density of particles with >1 μm diameter was <10/cm2. We suggest that an effective increase in surface temperature and deposition directly in the orthorhombic phase contributes to film quality.
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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
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Structure and composition of the 115 K superconducting phase in the Bi‐Ca‐Sr‐Cu‐O system

R. Ramesh, G. Thomas, S. M. Green, M. L. Rudee, and H. L. Luo

Appl. Phys. Lett. 53, 520 (1988); http://dx.doi.org/10.1063/1.100623 (3 pages) | Cited 7 times

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Results of convergent beam electron diffraction and energy dispersive x‐ray (EDX) microanalysis of Bi1.2Ca0.9Sr0.9Cu2Oy superconductor are reported. The structure is orthorhombic with a=5.63 Å, b=5.4 Å, and c=38.2 Å. The c parameter is different from those reported by other workers and suggests that two extra perovskite units ap, where ap=3.82 Å, have been introduced leading to c=10ap. EDX microanalysis shows that the Cu content of this phase is higher than that reported by other workers. It is suggested that the phase with c=38.2 Å may be the higher temperature (115 K) superconductor.
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74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds
74.25.Ha Magnetic properties including vortex structures and related phenomena

Multilayer deposition of Tl‐Ba‐Ca‐Cu‐O films

I. Shih and C. X. Qiu

Appl. Phys. Lett. 53, 523 (1988); http://dx.doi.org/10.1063/1.100624 (3 pages) | Cited 20 times

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Thin films of Tl‐Ba‐Ca‐Cu‐O with different atomic ratios and a thickness of about 2 μm have been prepared by a sequential thermal evaporation method on alumina substrates followed by a heat treatment in an environment containing O2 and Tl. The results showed that films with a superconducting onset temperature of about 120 K and a zero resistance temperature of 85 K can be obtained with the following Tl:Ca:Ba:Cu ratios: 2:2:2:3 or 2:2:2:4. Films with a superconducting transition onset at 115 K and a zero resistance temperature of 74 K were also obtained by heating Tl‐free multilayer films in the environment containing O2 and Tl. It was also found that this new material was more resistant to water.
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
74.10.+v Occurrence, potential candidates
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