FORTHCOMING PAPERS

The TI-Ba-Ca-Cu.O Superconducting Ceramics Containing AI20 3

T. Itoh, 1-1. Uchikawa (Japan) Nature of Contact Resistance in High-Tc YBa2Cu3OT_ 6 Superconductors

S. T. Lakshmikumar, A. C. Rastogi (India) The contacts between various metals and the high-Tc superconductor YBa2Cu307_6are characterized by contact resistance, R e and I--V measurements from 300 K to 90 K. The contacts with bulk superconductor were made by vacuum deposition. Four metals, Au, Ag, A1, and Bi were investigated. The current transport across the contact is by carrier tunneling. All contacts were ohmic as their I--V characteristics were symmetrical with respect to current direction. RcVaiues range between 1 0 - 2 t o 101 ~ cm2and increase linearly as the temperature is lowered. The contact resistance originates from two distinct physical processes. One is the modification of the carrier concentration at the interface by the contact metal. The second is the nature of carrier injection at the free surface of the superconductor. The Rcvalues depend on the contact metal-oxygen interaction parameter signifying the need for oxygen passivation for obtaining low contact resistances.

Effect of Process Parameters on the Properties of Plasma-Sprayed Superconducting YIBa2Cu3O 7 - - x Coatings

s Karthikeyan, 1(. P. Sreekumar, N. Venkatramani, M. B. Kurup, D. S. Patil, V. K. Rohatgi (India) A study on the effect of powder, spray and coating parameters on superconducting properties of plasma-sprayed Y1Ba2Cu307_x coatings has been carried out. Optimised spray parameters to yield strong, adherent and dense coatings on many substrates including AISI 304 SS and alumina have been obtained. Coatings show superconductivity after oxygen annealing at 950~ for an hour. Coatings thinner than 100 ~rn do not show zero resistivity down to 77 K due to weak links between granular superconductors. Coatings prepared with fine powder have superior superconducting properties, viz. higher Tc and Jc values than coarse powder coatings. The choice of substrate material strongly affects the Jc values.

Properties of RF Sputtered ZnxCdl_x S Thin Films

F.. El Akkad, 11. E Ragaie, M. A b d e l Naby (Saudi Arabia) ZnxCdl_xS thin films ( 0 ~ x _--<0.20) were prepared using rf sputtering in argon atmosphere and characterized using X-ray diffraction, optical transmission, electrical resistivity and photoconductive decay measurements. The films were found to possess hexagonal structure. The crystailite size and degree of preferential orientation were found to decrease with the increase of x and to improve u p o n annealing in vacuum at ~ 2 5 0 ~ The transmission edge shifted towards shorter wavelengths with the increase of x in agreement with the expected shift in the energy band gap. The films were found to exhibit room temperature resistivity in the range 100--1000 f2 cm. The obtained values of long wavelength transmission (70--80%) and minority carrier diffusion length ( ~ 30 ~-n) are high enough for the application of these films in the field of solar cells.

Interdiffusion, Reaction and Stability in a Thin Film Iron-Alnminium Bilayered System

S. R. Teixeira, F. L. Freire, Jr., L s R. Baumvol (Brasil) In this work we describe the results of Rutherford backscattering spectrometry, sheet resistivity measurements, X-ray diffractometry and conversion electron Mrssbaner spectroscopy performed on thin film Fe--Al bilayered samples submitted to high vacuum furnace annealing. Isothermal anneals were performed at 570 K for time intervals ranging 60 to 600 rain. It is demonstrated that the diffusion of A1 into Fe is smaller than the diffusion of Fe into Al for temperatures below 600 K. Sequential isochronous thermal anneals of 60 min were performed at temperatures ranging from 570 to 870 K, in order to study the stability of the formed phases. The stable Fe~2Al5 intermetallic compound formed at 570 K decomposes at about 650 K, and the FeAI 6 intermetallic compound appears at temperatures around 750 K.

The T1-Ba-Ca-Cu-O superconducting ceramics containing Al203 have been prepared utilizing the reaction, T120 3 + BaCuO 2 § Ca2CuO 3 + Al203 or T120 3 + BaCuO 3 + Ca2CuO 3 + A1CuO2. 5. It is shown that the resulting ceramics show the superconductivity at temperatures over 100 K when the A l / C u molar ratio is kept below 0.5. E P M A analyses revealed that there is always an A12BaO4 layer between the superconducting T1-Ba-Ca-Cu-O and A120 3 phases, leading to the separation between the superconducting and A120 3 phases. Nature of Oxygen in the Passive Film on Stainless Steels in 0.1M NaCI Solution

S. Jin, A. Atrens (Australia) Three different oxygen species, 0 2 _ O H - , and H 2 0 , are introduced into the deconvolution of the oxygen peaks measured in the prior study and their true concentrations are investigated in the depth profile, it is found that H 2 0 exists mainly in the outermost part of the passive film at the interface of solution and the passive film. O H - and 0 2 - are found throughout the passive film; they have a maximum concentrations in the outer layer at around 10 to 20 ~ depth, with a concentration of 40 at. 070 for the stainless steel 29-4-2 and 50 at.% for 18-12. After the maximum the concentration are sharply reduced with increasing sputtering time and remain at a constant concentration of about 10 at.% at 35 ~ depth. Both species still exist at this concentration even after long time sputtering.

Applied Physics B 48, No. 3 (1989) Invited Paper R. Meier, F. K. Kneubiihl, H. J. Sch~itzau Mass-Spectroscopic Study of the Influence of Nozzle Material on HighPressure SF6 Arcs 187

Contributed Papers A. Miki6s, A. Lrrincz Windowless Resonant Acoustic Chamber for Laser-Photoacoustic Applications 213 R. Renter, H . Franke A n Integrated Organic Photoconductive Detector for Optoelectronics 219 (;hen Zhihao, Qu Yah, Yao Huihai Birefringence and Polarization Mode Dispersion in Graded-Core StressApplied Polarization-Maintaining Fibers 225 S. Carusotto, E. Polaeco, E. Iaeopini, G. Stefauini, E. Zavattini, F. Scuri The Ellipticity Introduced by Interferential Mirrors on a Linearly Polarized Light Beam Orthogonally Reflected 231 H. Solka, W. Zimmermann, D. Relnert, A. Stahn, A. Dax, W. Urban A Simple Model for the Velocity Modulation Detection Technique of Molecular Ions 235 S. A. Bakilramov, A.T. Berdikulov, A. M. Kokharov, V. V. Tikhonenko Self-Induced Polarization Rotation of a Laser Beam in Resonance Media 243 J. A. Facin, D. Pcrcira, E. C. C. Vascouceilos, A. Sealabrin, C. A. Ferrari New FIR Laser Lines from CHD2OH Optically Pumped by a cw CO 2 Laser 245 E. M. Alonso, R. J. D'Angelo, E. J. Quel Studies of Vibrational Relaxation in CDF 3 Following Intense Laser Excitation 249 P. Simon Time-Resolved Ablation-Site Photography of XeC1-Laser Irradiated Polyimid 253 W. Quapp An Explanation of the Direction of the Relaxation in the H C N Gas Microwave Laser, and a New Assignment of Further Laser Lines Along the Path of Internal Vibrational Energy Redistribution 257 A. Mild6s, A. L6rincz Determination of Thermal Transport Properties of Thin Metal Films from Pulsed Thermoreflectance Measurements in the Picosecond Regime 261 A. C. Bento, M. M. F. Aguiar, I-I. Vargas, M. D. da Silva, I. N. Bandeira, L. C. M. Mirauda Open Photoacoustic Cell X-Ray Detection 269 D. N. Koziov, V. V. Smirnov, S. Yu. Volkov Study of Processes of Translational, Rotational, and Vibrational Relaxation Based on CARS Spectra Line Shapes 273

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