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20 Nov 1989

Volume 55, Issue 21, pp. 2161-2252

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External‐cavity coherent operation of InGaAsP buried‐heterostructure laser array

V. Diadiuk, Z. L. Liau, J. N. Walpole, J. W. Caunt, and R. C. Williamson

Appl. Phys. Lett. 55, 2161 (1989); http://dx.doi.org/10.1063/1.102087 (3 pages) | Cited 9 times

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Coherent operation of a monolithic linear array of InGaAsP buried‐heterostructure lasers operating at λ=1.3 μm has been acheived by means of a spatial filter in an external cavity. An array of mass‐transported InP microlenses was used to collimate the beams of the individual laser elements and couple the laser array output to the external cavity. The coherent array output exhibited a narrow (3.2 mrad), three‐lobe far‐field pattern with ∼65% of the energy concentrated in the central peak.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.55.Mv Dye lasers

Subpicosecond pulse generation from an all solid‐state laser

S. J. Keen and A. I. Ferguson

Appl. Phys. Lett. 55, 2164 (1989); http://dx.doi.org/10.1063/1.102088 (3 pages) | Cited 1 time

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We describe an all solid‐state (holosteric) laser source which produces subpicosecond pulses at 1.4 μm. The system consists of a diode laser pumped Nd:YAG laser which is frequency modulated (FM) mode locked and Q switched at 1.32 μm. In continuous wave operation the laser produces pulses of 19 ps while simultaneous Q switching and mode locking result in 30 ps pulses being contained in a Q‐switched envelope of energy 2.1 μJ. The output of the laser, when passed through a 1 km single‐mode optical fiber, produces a spectrally broad Raman signal with its peak at 1.4 μm and the overall conversion efficiency at 12%. The pulse duration at 1.4 μm has been measured to be 280 fs. We believe this is the first time that subpicosecond light pulses have been generated by an all solid‐state laser system.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Characterization of InGaAs‐GaAs strained‐layer lasers with quantum wells near the critical thickness

K. J. Beernink, P. K. York, J. J. Coleman, R. G. Waters, J. Kim, and C. M. Wayman

Appl. Phys. Lett. 55, 2167 (1989); http://dx.doi.org/10.1063/1.102089 (3 pages) | Cited 32 times

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Data are presented on the efficiency, reliability, and temperature dependence of wavelength and threshold for strained‐layer InxGa1−xAs‐GaAs (x∼0.25, λ>1.06 μm) separate confinement heterostructure lasers for several thicknesses near the critical thickness. Devices with well thicknesses of 100 Å exhibit excellent time‐zero characteristics and reliability, while those with 143 Å wells have higher initial thresholds and degrade rapidly.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Characterization of single‐crystal sapphire fibers for optical power delivery systems

D. H. Jundt, M. M. Fejer, and R. L. Byer

Appl. Phys. Lett. 55, 2170 (1989); http://dx.doi.org/10.1063/1.102348 (3 pages) | Cited 28 times

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Sapphire single‐crystal fibers with diameters of 110 μm and lengths of over 2 m have been grown by the laser‐heated pedestal growth method. The fibers are free of imperfections such as voids and bubbles. The minimum loss of 0.5 dB/m was measured in the near infrared at 1064 nm. Absorption loss at 2936 nm was 0.88 dB/m with a damage threshold higher than 1.2 kJ/cm2 for 110‐μs‐long pulses making tissue ablation feasible with fibers several meters in length.
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42.81.Dp Propagation, scattering, and losses; solitons
42.70.-a Optical materials
81.40.Tv Optical and dielectric properties related to treatment conditions
61.72.jn Color centers

High‐speed metal‐semiconductor‐metal waveguide photodetector on InP

J. B. D. Soole, H. Schumacher, R. Esagui, H. P. LeBlanc, R. Bhat, and M. A. Koza

Appl. Phys. Lett. 55, 2173 (1989); http://dx.doi.org/10.1063/1.102073 (3 pages) | Cited 5 times

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We demonstrate high‐speed performance of InGaAs barrier‐enhanced metal‐semiconductor‐metal (M‐S‐M) Schottky barrier photodetectors monolithically integrated with double‐heterostructure InP/InGaAsP/InP waveguides. Pulse response widths of 77 ps are recorded, with an associated 3 dB power bandwidth of 1.7 GHz. Photodetectors acting as both ‘‘taps’’ of the waveguided signal and as ‘‘terminal’’ devices were fabricated. These detectors have application in receivers which are integrated with semiconductor waveguides for on‐chip optical signal processing.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Gn Optical waveguides and couplers
73.40.Sx Metal-semiconductor-metal structures
42.82.-m Integrated optics

Electron beam excitation of rare‐gas alkali ionic excimers

P. S. Millar, G. Warwar, P. J. Wisoff, R. Sauerbrey, and K. Balasubramanian

Appl. Phys. Lett. 55, 2176 (1989); http://dx.doi.org/10.1063/1.102349 (3 pages) | Cited 18 times

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The observation of fluorescence from ionic rare‐gas alkali molecules excited by an electron beam is reported. Gas mixtures of argon and xenon with hot vapors of either rubidium or cesium were excited to obtain emission from (XeRb)+ at 164 nm and (XeCs)+ at 160 nm. The spectral features observed in (XeRb)+ are assigned to three upper electronic states.
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33.50.Dq Fluorescence and phosphorescence spectra
34.80.Gs Molecular excitation and ionization
33.20.Ni Vacuum ultraviolet spectra
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Effects of oxygen on diamond growth

Stephen J. Harris and Anita M. Weiner

Appl. Phys. Lett. 55, 2179 (1989); http://dx.doi.org/10.1063/1.102350 (3 pages) | Cited 79 times

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In situ mass spectral measurements of gas composition at the substrate surface were made during filament‐assisted diamond growth. The input gases were various mixtures of CH4, O2, and H2 chosen in order to discern the effects of oxygen addition on diamond formation and growth. The gas phase chemistry was modeled as a one‐dimensional flow reactor, and the measured and calculated species mole fractions were in good agreement. The model was then used to estimate mole fractions of several atomic and radical species which could not be measured. We find that addition of O2 has only a small effect on the radical mole fractions. However, O2 can reduce the effective initial hydrocarbon mole fraction, which is important because higher quality diamond is grown at a lower initial hydrocarbon mole fraction. Most important, perhaps is that O2 addition leads to the formation of sufficient gas phase OH to remove nondiamond (pyrolytic) carbon from the film. Thus, O2 addition allows diamond films to be grown under composition and temperature conditions which otherwise would produce largely nondiamond carbon.
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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
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

New dual‐bath technique for electrodeposition of short repeat length multilayers

L. M. Goldman, C. A. Ross, W. Ohashi, D. Wu, and F. Spaepen

Appl. Phys. Lett. 55, 2182 (1989); http://dx.doi.org/10.1063/1.102351 (3 pages) | Cited 12 times

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An electrodeposition technique for making multilayered thin films, based on controlled deposition from two different solutions, is described. Ni/NiPx and NiPx/NiPy multilayered thin films with repeat lengths as low as 20 Å have been prepared. They show up to three low‐angle x‐ray peaks corresponding to the electron density modulation.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
82.45.-h Electrochemistry and electrophoresis

Mobility of silver on tin oxide surfaces

W. M. Sears and Konrad Colbow

Appl. Phys. Lett. 55, 2185 (1989); http://dx.doi.org/10.1063/1.102074 (2 pages) | Cited 5 times

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We report on the observation of the rapid drift mobility of metallic silver under an applied electric field on the surface of a pyrolitically deposited tin oxide film. Silver dag contacts were applied to the surface of the film which was maintained in air at a temperature of 330 °C under a potential difference of a few volts. Under these conditions metallic silver was seen to migrate across the film forming both fractal and dense packed structures.
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66.30.Qa Electromigration
66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)

Crack formation and thermal stress relaxation of GaAs on Si growth by metalorganic vapor phase epitaxy

A. Ackaert, L. Buydens, D. Lootens, P. Van Daele, and P. Demeester

Appl. Phys. Lett. 55, 2187 (1989); http://dx.doi.org/10.1063/1.102056 (3 pages) | Cited 5 times

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In this letter we report on the use of selective metalorganic vapor phase epitaxy growth as an original tool to alleviate the problem of random formation of microcracks in thick GaAs‐on‐Si heteroepitaxial layers. Through the use of a special mask design including the definition of sharp wedges in the SiO2 mask material, the thermally induced stress in the GaAs‐on‐Si layers preferentially relaxes at precisely located sites on the substrate. The influence of mask configuration, wedge shape, wedge orientation, and layer thickness on microcrack formation has been investigated. Results obtained show that small‐area SiO2 wedges are useful for the definition of microcrack location, and thus eventually for optoelectronic device processing.
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68.60.Bs Mechanical and acoustical properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
85.40.Hp Lithography, masks and pattern transfer
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

X‐ray investigation of the ordered structure in AlGaInP quaternary alloys

Hiroshi Okuda, Chikashi Anayama, Toshiyuki Tanahashi, and Kazuo Nakajima

Appl. Phys. Lett. 55, 2190 (1989); http://dx.doi.org/10.1063/1.102057 (3 pages) | Cited 2 times

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The ordered structure occurring in AlGaInP quaternary alloys grown on GaAs substrates by low‐pressure metalorganic vapor phase epitaxy has been investigated by means of x‐ray diffraction measurements. The order spot became strong as the Al content increased, and was observed only for the (1/2 ∼(1/2) 1/2) diffraction, corresponding to CuPt‐type (111)B ordering. Kinematical analysis implies that the full width at half maximum of the order spot is strongly affected by the antiphase boundary, whereas the integrated intensity is not.
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68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.05.C- X-ray diffraction and scattering

Optical spectroscopy and field‐enhanced emission of an oxide trap induced by hot‐hole injection in a silicon metal‐oxide‐semiconductor field‐effect transistor

M. Bourcerie, J. C. Marchetaux, A. Boudou, and D. Vuillaume

Appl. Phys. Lett. 55, 2193 (1989); http://dx.doi.org/10.1063/1.102058 (3 pages) | Cited 9 times

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The oxide traps created by hot‐hole injection in the thin gate oxide of n‐type metal‐oxide‐semiconductor transistor are optically and electrically characterized. Photodepopulation spectroscopy is used to investigate their photodetrapping kinetics. A threshold at 3 eV is found for the photoionization cross section. The effect of the electric field on the emission is analyzed using the Poole–Frenkel model. We show that a localized energy level in the range 2–3 eV below the SiO2 conduction band is associated with trap. It is spatially localized above the drain region of the transistor.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optical depth profiling of ion beam etching induced damage in InGaAs/InP heterostructures

R. Germann, A. Forchel, and D. Grützmacher

Appl. Phys. Lett. 55, 2196 (1989); http://dx.doi.org/10.1063/1.102059 (3 pages) | Cited 4 times

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We have investigated the energy dependence and depth distribution of the damage caused by ion beam etching using Ar/O2−ions with energies in the range between 175 and 1200 eV. The damage was created by partially etching the upper InP barrier of In0.53Ga0.47As single quantum wells. The optical emission from the quantum wells is used as a high‐resolution local probe for the damage. From the decay of the quantum efficiency as a function of the etch depth we determine an effective damage range of about 8.4 nm for 250 eV ions in InP.
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61.80.Jh Ion radiation effects
81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Infrared absorption and Raman scattering by plasmons in thin layers of GaAs grown by molecular beam epitaxy

D. Kirillov, D. Liu, and Shang‐Lin Weng

Appl. Phys. Lett. 55, 2199 (1989); http://dx.doi.org/10.1063/1.102060 (3 pages) | Cited 2 times

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Infrared absorption at oblique incidence and Raman scattering were used to measure plasmon spectra in highly doped n‐type GaAs layers grown by molecular beam epitaxy. Plasmon frequency was lower in infrared absorption spectra compared to Raman spectra of the same samples due to the wave vector dependence of the plasmon frequency. The linewidth of plasmon lines was quite similar in infrared absorption and Raman scattering spectra, indicating the small role of Landau damping for the studied range of wave vectors. Infrared plasmon absorption was strongly reduced for films thicker than the wavelength of plasmons, and the wave vector dependence was reduced for very thin films when the electron gas started to acquire quasi‐two‐dimensional character.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen

J. R. Engstrom, D. J. Bonser, and Thomas Engel

Appl. Phys. Lett. 55, 2202 (1989); http://dx.doi.org/10.1063/1.102352 (3 pages) | Cited 6 times

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The effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen has been examined under ultrahigh vacuum conditions by employing molecular beam techniques and x‐ray photoelectron spectroscopy. Ion bombardment leads to a significant enhancement in the rate of oxidation. By modulating both the oxygen and ion (Ar+ ) fluxes several possible mechanisms for the enhanced rate can be eliminated. Of the remaining possibilities, a mechanism involving competition between ion‐induced oxygen incorporation and sputtering appears most likely.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.80.Jh Ion radiation effects
34.50.Lf Chemical reactions

Novel technique for Si epitaxial lateral overgrowth: Tunnel epitaxy

Atsushi Ogura and Yuki Fujimoto

Appl. Phys. Lett. 55, 2205 (1989); http://dx.doi.org/10.1063/1.102061 (3 pages) | Cited 7 times

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A novel technique for Si epitaxial lateral overgrowth, called tunnel epitaxy, is proposed and demonstrated. In this technique, lateral epitaxy proceeds in the tunnel between the upper and lower SiO2 layers. Limitation of film thickness is achieved, as is a high lateral/vertical growth ratio of approximately 7. Lateral growth distance is limited by clogging of the gas injection window by polycrystalline Si grain growth. Rough surface morphology and twin boundary defects were observed in the fabricated silicon‐on‐insulator. The origins of and possible solutions for these problems are discussed.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Organometallic vapor phase epitaxial growth of GaAs‐based pseudomorphic modulation‐doped field‐effect transistor structures

Alan G. Thompson, Bor‐Yen Mao, and Gi Young Lee

Appl. Phys. Lett. 55, 2208 (1989); http://dx.doi.org/10.1063/1.102062 (3 pages) | Cited 1 time

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We report the preparation of InGaAs/AlGaAs strained‐layer(pseudomorphic) modulation‐doped field‐effect transistor (MODFET) structures by organometallic vapor phase epitaxy (OMVPE). Devices fabricated from these structures with 0.9 μm gate lengths had dc extrinsic transconductances up to 340 mS/mm. Microwave testing up to 40 GHz showed current gain cutoff frequencies ( fT ) of 22 GHz and estimated maximum frequency of oscillation ( fmax ) of 70 GHz. This is the first report to our knowledge of the use of OMVPE material in the fabrication of pseudomorphic MODFETs.
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85.30.Tv Field effect devices
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Conduction‐band offset in strained Al0.15Ga0.85As/In0.15Ga0.85As/GaAs pseudomorphic structures

S. Y. Lin, D. C. Tsui, H. Lee, and D. Ackley

Appl. Phys. Lett. 55, 2211 (1989); http://dx.doi.org/10.1063/1.102063 (3 pages) | Cited 7 times

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We report a first determination of the conduction‐band offset in the strained‐layer Al0.15Ga0.85As/In0.15Ga0.85As/GaAs pseudomorphic structure. Two‐dimensional electron density and its effective mass are independently measured by Shubnikov–de Haas and cyclotron resonance experiments for a series of samples with a range of spacer thickness from 30 to 100 Å. Using a charge transfer model, the conduction‐band offset at the Al0.15Ga0.85As/In0.15Ga0.85As interface is found to be (255±35) meV.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
76.40.+b Diamagnetic and cyclotron resonances

Electrical characteristics of regrown interfaces using diethylgallium chloride‐based metalorganic vapor phase epitaxy

M. A. Tischler, T. F. Kuech, A. Palevski, and P. Solomon

Appl. Phys. Lett. 55, 2214 (1989); http://dx.doi.org/10.1063/1.102064 (3 pages) | Cited 2 times

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The electrical characteristics of regrown interfaces deposited using an alternate metalorganic chemistry, diethylgallium chloride (DEGaCl), are investigated. With the appropriate HCl pre‐regrowth surface treatment, these interfaces are found to be of very high quality with no substantial interface charge. The contact resistivity, as determined by transmission line measurements, is (2–4)×10−7 Ω cm2 at both 77 and 300 K. Secondary‐ion mass spectroscopy measurements show no detectable accumulation of impurities at the regrown interface, in contrast to those regrown using the conventional trimethylgallium‐based chemistry.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
68.35.Dv Composition, segregation; defects and impurities
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Fluctuating deep level trap occupancy model for bulk 1/f noise in field‐effect transistors

P. A. Folkes

Appl. Phys. Lett. 55, 2217 (1989); http://dx.doi.org/10.1063/1.102065 (3 pages) | Cited 4 times

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A quantitative theoretical model for bulk 1/f noise in semiconductor resistors has been developed. The model uses the fact that random fluctuations of the steady‐state deep level trapped electron density at some point in a depletion layer decay exponentially with a time constant which depends on the local free‐electron density. The model was used to derive an exact integral expression and a simple approximate analytic expression for the spectral density of bulk 1/f and generation noise in unsaturated field‐effect transistors. Excellent agreement with experimental results is obtained. The relationship between bulk 1/f and generation noise spectra is discussed.
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72.70.+m Noise processes and phenomena
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
85.30.Tv Field effect devices
71.55.Eq III-V semiconductors

Highly stable W/p‐In0.53Ga0.47As ohmic contacts formed by rapid thermal processing

A. Katz, B. E. Weir, D. M. Maher, P. M. Thomas, M. Soler, W. C. Dautremont‐Smith, R. F. Karlicek, J. D. Wynn, and L. C. Kimerling

Appl. Phys. Lett. 55, 2220 (1989); http://dx.doi.org/10.1063/1.102066 (3 pages) | Cited 14 times

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Tungsten contacts to Zn‐doped In0.53Ga0.47As have been formed by rapid thermal processing. Contacts to layers with a Zn doping concentration of 5×1018 cm−3 were rectifying as sputter deposited as well as after heat treatments at temperatures lower than 450 °C. Higher processing temperatures caused a linear decrease of the contact resistivity values from 0.6 as deposited to 0.15 Ω mm after heating at 550 °C. Rapid thermal processing at these higher temperatures stimulated the Schottky‐to‐ohmic contact conversion with a minimum contact resistance value of 8.5×10−5 Ω cm2 and a sheet resistance value of 150 Ω/☒ as a result of heating at 600 °C for 30 s. By increasing the p‐InGaAs doping level to 1×1019 cm−3, the specific resistance of this contact was dropped to the minimum of 7.5×10−6 Ω cm2 as a result of heating at 600 °C for 30 s. The W/p‐In0.53Ga0.47As contact showed excellent thermal stability over the temperature range of 300–750 °C, with an abrupt and almost unreacted metal‐semiconductor interface. Heating at temperatures of 800 °C or higher caused degradation of the contact. This was reflected by a distinct increase in the heterostructure sheet resistance as a result of the intensive interfacial reaction which took place at the contact, accompanied by outdiffusion of both In and As.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
81.40.Rs Electrical and magnetic properties related to treatment conditions
73.25.+i Surface conductivity and carrier phenomena

Novel semiconductor substrate formed by hydrogen ion implantation into silicon

Jianming Li

Appl. Phys. Lett. 55, 2223 (1989); http://dx.doi.org/10.1063/1.102067 (2 pages) | Cited 15 times

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See Also: Erratum

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A high‐resistivity layer formed beneath the silicon surface layer by using proton implantation and two‐step annealing is described. Rapid thermal annealing with tungsten halogen lamps was carried out during the first annealing step and the time of the high‐temperature treatment in the second annealing step was comparatively long. Experiments show that the quality of the top layer has been improved with the increase in surface Hall mobility of ∼25%. This novel semiconductor will likely be a new material for the manufacture of very high speed integrated circuits.
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61.72.uf Ge and Si
72.80.Cw Elemental semiconductors
85.40.Hp Lithography, masks and pattern transfer
61.72.Bb Theories and models of crystal defects

In situ reflectivity measurement in a rapid thermal processor for the study of platinum silicide formation

Jean‐Marie Dilhac, Christian Ganibal, and Thierry Castan

Appl. Phys. Lett. 55, 2225 (1989); http://dx.doi.org/10.1063/1.102068 (2 pages) | Cited 2 times

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The reflectivity of thin‐film platinum silicide was measured by means of a helium‐neon (He‐Ne) laser when samples of platinum films deposited on top of silicon wafers were annealed in a rapid thermal processor. This processor consists of two rows of tungsten‐halogen quartz lamps placed above and below a quartz processing chamber. The thermal cycles consisted of a fast heating (about 200 °C/s), followed by an isothermal plateau at temperatures ranging between 410 and 600 °C. Film reflectivities dropped in two stages, as a result of the reaction between platinum and silicon. This two‐stage drop was identified as due to the transformation of the platinum film, first into Pt2Si, and then into PtSi. The amounts of time required to complete the transformations were found to be in good agreement with the Arrhenius laws derived from the work of J. T. Pan and I. A. Blech [Thin Solid Films 113, 129 (1984)] on isothermal low‐temperature (220–330 °C) sintering of platinum films on silicon, who unambiguously established the correlation between reflectivity changes and silicide formation.
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78.66.-w Optical properties of specific thin films
68.55.Nq Composition and phase identification

Synthesis of Bi‐Pb‐Sr‐Ca‐Cu oxide/Ag superconductors by melt dipping and oxidation of metallic precursor alloys

W. Gao, S‐C. Li, D. A. Rudman, G. J. Yurek, and J. B. Vander Sande

Appl. Phys. Lett. 55, 2227 (1989); http://dx.doi.org/10.1063/1.102353 (3 pages) | Cited 4 times

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Bi‐Pb‐Sr‐Ca‐Cu‐Ag alloy coatings were made by vacuum induction melting followed by melt dipping on substrates of MgO, SrTiO3, and Al2O3. The metallic precursor layers were then subjected to a controlled atmosphere oxidation and annealing to produce oxide superconductors. Superconducting coatings with onset temperatures of 112 K and zero resistance temperatures of 80 K were obtained in this way. The addition of Ag aided in the alloy melting and dipping processes, and produced a superconducting oxide/noble metal composite after oxidation. The resulting superconducting phases were analyzed by x‐ray powder diffraction. The influence of the substrate, dipping processes, oxidation, and annealing conditions on the superconducting properties are discussed.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.40.Rs Electrical and magnetic properties related to treatment conditions

Surface roughening associated with ∼140 °C transition of a LaGaO3 substrate for high Tc superconducting films

Shintaro Miyazawa

Appl. Phys. Lett. 55, 2230 (1989); http://dx.doi.org/10.1063/1.102354 (3 pages) | Cited 22 times

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A ferroelastic‐like transition at ∼140 °C in a single‐crystal LaGaO3 substrate was directly observed with an optical microscope at elevated temperatures. In addition, it was found for the first time that a polished surface morphology of a pseudocubic (001) LaGaO3 substrate degraded after a heat cycle up to only 200 °C. This surface degradation, i.e., surface roughening, is associated with the transition at ∼140 °C, and it may possibly be the major origin of relatively low critical current density reported for a superconducting YBa2Cu3Ox film grown on a LaGaO3 substrate.
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68.35.Rh Phase transitions and critical phenomena
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
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