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25 Jun 1990

Volume 56, Issue 26, pp. 2599-2698

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Depth profiling of a silicon nitride layer by 20 keV N+2 ion implantation through an oxide layer as seen by x‐ray photoelectron spectroscopy

A. Ermolieff, P. Molle, and S. Marthon

Appl. Phys. Lett. 56, 2672 (1990); http://dx.doi.org/10.1063/1.103266 (3 pages) | Cited 2 times

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The chemical composition profile of a nitride layer obtained by 20 keV N+2 ion implantation through an oxide layer was determined by x‐ray photoelectron spectroscopy at two different analysis angles. The nitrogen concentration shows a plateau followed by a slow decrease. Oxygen, presumably due to a recoil implantation, is always present in the nitride layer in exponentially decreasing amounts. The film is composed of elemental silicon, silicon oxynitride, and diffused oxygen. The respective concentrations of the two silicon components are nearly constant and the diffused oxygen decreases. In the interface region, the oxynitride loses its oxygen progressively; at the very end of the interface, nitrogen seems to be partially chemisorbed. In a sample which has undergone a double annealing, the oxygen diffuses deeper in the bulk of the substrate.
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81.65.-b Surface treatments
33.60.+q Photoelectron spectra
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

High transport critical currents and flux jumps in bulk YBa2Cu3Ox superconductors

K. Chen, S. W. Hsu, T. L. Chen, S. D. Lan, W. H. Lee, and P. T. Wu

Appl. Phys. Lett. 56, 2675 (1990); http://dx.doi.org/10.1063/1.103267 (3 pages) | Cited 27 times

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A preferentially oriented bulk YBa2Cu3Ox superconductor was prepared by the liquid phase method. A continuous dc current carrying capacity exceeding 120 A with current density higher than 37 300 A/cm2 at 77 K has been obtained. The high current effects causing fracture of the sample were studied in relation to the thermal diffusion properties. In magnetization measurements, flux jumps were observed for currents in the sample a‐b plane below the temperature of about 20 K. The jumps are more closely spaced with decreasing temperature or increasing field sweep rates.
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates

Electrical characterization of chemically modified YBa2Cu3O7−x surfaces

B. D. Hunt, M. C. Foote, and R. P. Vasquez

Appl. Phys. Lett. 56, 2678 (1990); http://dx.doi.org/10.1063/1.103268 (3 pages) | Cited 5 times

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Results on electrical characterization of YBa2Cu3O7−x thin‐film surfaces treated with a Br/ethanol chemical etch are presented. Electrical measurements of YBa2Cu3O7−x/Au/Nb device structures fabricated using polycrystalline, post‐annealed YBa2Cu3O7−x films with Br‐etched surfaces, show improvements of approximately one or two orders of magnitude in current densities and resistivities (resistance‐area products) relative to unetched devices. The existence of supercurrents in these structures has been confirmed by observation of the ac Josephson effect, and by magnetic field and temperature studies of the critical currents. The Br‐etch process has produced 10×10 μm2 devices with critical current densities greater than 400 A/cm2 and resistivities as low as 4×10−7 Ω cm2.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
85.25.Cp Josephson devices

Critical currents in proton‐irradiated single‐crystal Ba2YCu3O7−δ

R. B. van Dover, E. M. Gyorgy, A. E. White, L. F. Schneemeyer, R. J. Felder, and J. V. Waszczak

Appl. Phys. Lett. 56, 2681 (1990); http://dx.doi.org/10.1063/1.103269 (3 pages) | Cited 47 times

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Irradiation with 3.5 MeV protons creates defects in Ba2YCu3O7−δ, which can act as strong pinning sites, comparable to those produced by neutron irradiation. Indeed protons as well as neutrons undergo momentum‐transferring collisions that result in atomic displacements; the additional electronic proton‐solid interaction does not appear to yield defects which contribute to pinning. Under optimized conditions we have obtained Jc(T→0, H=1 T)∼2×107 A/cm2 in single crystals. At 77 K the value is still Jc∼1.7×105 A/cm2, decreasing only threefold in a field of 6 T. The fluence and temperature dependence of Jc suggest a model, in which spatially uncorrelated defects pin vortex cores.
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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
61.80.Jh Ion radiation effects

Superconducting YBa2Cu3O6.8 films on metallic substrates using in situ laser deposition

E. Narumi, L. W. Song, F. Yang, S. Patel, Y. H. Kao, and D. T. Shaw

Appl. Phys. Lett. 56, 2684 (1990); http://dx.doi.org/10.1063/1.103270 (3 pages) | Cited 26 times

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In situ laser deposition was used to fabricate YBa2Cu3O6.8 (YBCO) films on metallic substrates. With a buffer layer, YBCO films were strongly c‐axis oriented. Tc = 83 K and Jc= 4000 A/cm2 at 77 K were obtained for a 0.5 μm YBCO film with a 0.15 μm yttrium‐stabilized ZrO2 buffer layer. There was negligible interdiffusion occurring at the interfaces. The n value of YBCO films ranged from 1.4 to 1.5.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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
74.78.-w Superconducting films and low-dimensional structures

Role of the substrate in enhancing the magneto‐optic response of ultrathin films: Fe on Au

E. R. Moog, S. D. Bader, and J. Zak

Appl. Phys. Lett. 56, 2687 (1990); http://dx.doi.org/10.1063/1.102827 (3 pages) | Cited 20 times

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Simulations are presented for the magneto‐optic rotation and ellipticity as a function of Fe thickness in the 0–400 Å range for the system Fe on Au (100). The results, which are based on tabulated bulk optical constants, agree with recent experiments and explicitly demonstrate the role of the Au underlayer in enhancing the signal from the ferromagnetic overlayer.
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78.20.Ls Magneto-optical effects
78.66.Bz Metals and metallic alloys
75.70.Rf Surface magnetism

Direct overwriting capability in TM‐rich side rare‐earth transition metal amorphous films

Shinji Takayama, Teruhisa Shimizu, Soichi Owa, and Hiroshi Tanaka

Appl. Phys. Lett. 56, 2690 (1990); http://dx.doi.org/10.1063/1.102828 (3 pages)

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The feasibility of a new method for direct overwrite with a power‐modulated laser beam under a constant external bias field Hex fixed in the same direction as an initializing field Hinit was demonstrated by means of a dynamic disk tester. TbFeCoCr amorphous films with compensation temperature (Tcomp) far below room temperature were employed, but coercivity falls below 200 Oe at 200 °C, while the saturation magnetization remains high. We found that written pits are formed by a demagnetization field Hd in the region of a weak Hex, whereas for a stronger Hex they are formed by a effective external field Heff(=Hex−Hd) fixed in the same direction as Hinit. By using a power modulation between 9 and 5 mW under a constant field of −100 Oe, we were able to demonstrate direct overwrite, although the readout carrier‐to‐noise ratio was low (18 dB).
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85.70.Sq Magnetooptical devices
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ch Domain walls and domain structure

Surface melting of metal deposits during laser‐induced chemical vapor deposition with a modulated continuous‐wave laser

Paul B. Comita, Peter E. Price, and Toivo T. Kodas

Appl. Phys. Lett. 56, 2693 (1990); http://dx.doi.org/10.1063/1.102829 (3 pages) | Cited 3 times

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Thermal laser‐induced chemical vapor deposition of gold crystals on alumina substrates has been studied using a modulated Ar+ laser. Deposition of gold from dimethylgold hexafluoroacetylacetonate is accompanied by surface melting of the deposit when the laser source is modulated. Time‐resolved reflectance measurements have been used to study the time evolution of the surface reflectance during growth with both modulated and unmodulated laser light. These experiments suggest that the surface melting observed with a modulated laser source is primarily due to the heat released by the exothermic decomposition of reactant adsorbed on the surface during the time that the laser intensity is off.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.47.-p Spectroscopy of solid state dynamics
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

View on linking the particle backscattering and particle‐induced x‐ray emission methods of materials analysis

A. Li‐Scholz, W. Scholz, and K. A. Stevenson

Appl. Phys. Lett. 56, 2696 (1990); http://dx.doi.org/10.1063/1.102830 (3 pages)

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A method employing simultaneous counting of elastically backscattered ions and particle‐induced x rays is demonstrated as a particularly simple means of measuring differential non‐Rutherford proton scattering cross sections. This method eliminates the need to determine total projectile number, target atom density or detector solid angles, or to use any additional reference element. Applied to elemental analysis via x rays, this method should allow equal accuracy to be attained with L x rays as with K x rays. The method’s simplicity and versatility in these applications suggest the routine linking of the two materials analysis techniques in an integrated system which lends itself to successively reducing the impact of residual uncertainties in inner shell ionization cross sections.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.85.-m X- and γ-ray instruments
78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter (restricted to new topics in section 78)
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