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Title: Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films

Abstract

Twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7–x} films with a thickness less than 40 nm have been epitaxially grown on (100)SrLaGaO{sub 4} crystals. Based on the temperature dependence of resistance, the onset temperature of the transition to the superconducting state is found to be 90 K; the transition width is 4 K. The film growth has been performed in two stages. A (100)PrBa{sub 2}Cu{sub 3}O{sub 7–x} buffer layer was previously grown on a (100)SrLaGaO{sub 4} substrate by rf magnetron sputtering in an Ar–O{sub 2} gas mixture at a continuous and monotonic increase in temperature from 660 to 830°C. The main YBa{sub 2}Cu{sub 3}O{sub 7–x} film was grown on the buffer layer surface by pulsed laser deposition in an oxygen medium at a fixed temperature (800°C). The above processes were implemented in different chambers, which were connected by a vacuum channel for transporting samples. Both films were grown in situ, without contacting atmosphere in all growth stages. An X-ray diffraction study has shown that the YBa{sub 2}Cu{sub 3}O{sub 7–x} films are single-crystal and free of precipitates of other phases and domains of other orientations.

Authors:
 [1]; ;  [2]
  1. Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation)
  2. Chalmers University of Technology, Department of Microtechnology and Nanoscience (Sweden)
Publication Date:
OSTI Identifier:
22645255
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 62; Journal Issue: 1; Other Information: Copyright (c) 2017 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BARIUM COMPOUNDS; CUPRATES; ENERGY BEAM DEPOSITION; EPITAXY; FILMS; LASER RADIATION; MAGNETRONS; MONOCRYSTALS; PULSED IRRADIATION; X-RAY DIFFRACTION; YTTRIUM COMPOUNDS

Citation Formats

Stepantsov, E. A., E-mail: stepantsov@ns.crys.ras.ru, Arpaia, R., and Lombardi, F.. Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films. United States: N. p., 2017. Web. doi:10.1134/S1063774517010242.
Stepantsov, E. A., E-mail: stepantsov@ns.crys.ras.ru, Arpaia, R., & Lombardi, F.. Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films. United States. doi:10.1134/S1063774517010242.
Stepantsov, E. A., E-mail: stepantsov@ns.crys.ras.ru, Arpaia, R., and Lombardi, F.. Sun . "Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films". United States. doi:10.1134/S1063774517010242.
@article{osti_22645255,
title = {Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films},
author = {Stepantsov, E. A., E-mail: stepantsov@ns.crys.ras.ru and Arpaia, R. and Lombardi, F.},
abstractNote = {Twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7–x} films with a thickness less than 40 nm have been epitaxially grown on (100)SrLaGaO{sub 4} crystals. Based on the temperature dependence of resistance, the onset temperature of the transition to the superconducting state is found to be 90 K; the transition width is 4 K. The film growth has been performed in two stages. A (100)PrBa{sub 2}Cu{sub 3}O{sub 7–x} buffer layer was previously grown on a (100)SrLaGaO{sub 4} substrate by rf magnetron sputtering in an Ar–O{sub 2} gas mixture at a continuous and monotonic increase in temperature from 660 to 830°C. The main YBa{sub 2}Cu{sub 3}O{sub 7–x} film was grown on the buffer layer surface by pulsed laser deposition in an oxygen medium at a fixed temperature (800°C). The above processes were implemented in different chambers, which were connected by a vacuum channel for transporting samples. Both films were grown in situ, without contacting atmosphere in all growth stages. An X-ray diffraction study has shown that the YBa{sub 2}Cu{sub 3}O{sub 7–x} films are single-crystal and free of precipitates of other phases and domains of other orientations.},
doi = {10.1134/S1063774517010242},
journal = {Crystallography Reports},
number = 1,
volume = 62,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2017},
month = {Sun Jan 15 00:00:00 EST 2017}
}
  • YBa{sub 2}Cu{sub 3}O{sub 7−x} films of b orientation have been grown on the surface of (100)SrLaGaO{sub 4} crystal. It is demonstrated that the films pass to the superconducting state at a temperature of 89 K. In the nonsuper-conducting region, the film resistance decreases linearly with a decrease in temperature at a rate of 30 Ω per 100°C. According to the X-ray diffraction data on the crystallographic structure of the YBa{sub 2}Cu{sub 3}O{sub 7−x} films, they are single-crystal and b-oriented. It is shown that the films contain no domains of other crystallographic orientations, including a-oriented domains. Therefore, the films are freemore » of structural twins.« less
  • Precise measurement of the temperature and voltage dependence of junction conductance has been carried out for {ital a},{ital b}-axis-oriented YBa{sub 2}Cu{sub 3}O{sub 7}/PrBa{sub 2}Cu{sub 3}O{sub 7}/YBa{sub 2}Cu{sub 3}O{sub 7} sandwich-type junctions to investigate the possible origin of Josephson coupling in these junctions. Regardless of the presence or absence of the Josephson effect, most of the junctions exhibited a dip in conductance around zero voltage in their {ital dI}/{ital dV} profiles at low temperatures. This {ital dI}/{ital dV} anomaly was attributed to the existence of a minimum in the density of states due to electron-electron interaction in disordered metals in themore » vicinity of a tunneling barrier within the junctions. The complex temperature dependence of junction conductance was reproduced well by a theoretical model in which both tunneling conduction paths and variable range hopping paths were assumed to exist within the PrBa{sub 2}Cu{sub 3}O{sub 7} barrier layer. No definite evidence of current transport through a small number of localized levels or a metallic conduction path in PrBa{sub 2}Cu{sub 3}O{sub 7} has been confirmed, even for junctions with a 20-nm-thick barrier layer. {copyright} {ital 1996 The American Physical Society.}« less
  • The structure of YBa{sub 2}Cu{sub 3}O{sub {ital x}} thin films and YBa{sub 2}Cu{sub 3}O{sub {ital x}}/PrBa{sub 2}Cu{sub 3}O{sub {ital x}} superlattice films grown on (00{ital L}) SrTiO{sub 3} substrates has been studied using x-ray diffraction and transmission electron microscopy. The films consist of four symmetry-equivalent domains related by mutually perpendicular ({ital hh}0) and ({ital h{bar h}}0) twin boundaries. One twin orientation is often highly favored over the other. We have correlated this in-plane symmetry breaking with small miscuts of the substrate surface towards the ({ital HH}0) direction and propose that interfacial steps act as nucleation sites for twins. Thus, bymore » controlling the surface normal, a technique is described for producing films containing aligned twin boundaries.« less
  • The authors report on the preparation and characterization of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}/PrBa{sub 2}Cu{sub 3}O{sub 7{minus}x} bilayers onto (100) SrTiO{sub 3} substrates. The samples have been prepared by sequential dc sputtering processes in high oxygen pressure from stoichiometric targets. The structural characterization of the YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} and PrBa{sub 2}Cu{sub 3}O{sup 7{minus}x} films and of the bilayers has been performed by means of X-ray diffraction. The Scanning Electron Microscopy analysis has showed that the film surfaces are flat and free of precipitates. A detailed study of the interfaces has been performed by Transmission Electron Microscopy analysis. The electrical resistivitymore » measurements showed for the YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} films sharp superconducting transitions at 91.5 K and critical current density of about 10{sup 6} A/cm{sup 2} at 77 K, while for the PrBa{sub 2}Cu{sub 3}O{sub 7{minus}x} films a semiconductor-like behavior has been observed.« less
  • We have measured the resistivity tensor in one nearly twin-free crystal and one twin-free crystal of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. The first crystal was grown with a large twin-free region. We removed the twins in the second crystal by applying a uniaxial stress. Using a modified Montgomery technique, we measured the electrical resistivities in all three crystal directions and found them to be linear in temperature above the superconducting transition temperature {ital T}{sub {ital c}}. Our results for {rho}{sub {ital a}} and {rho}{sub {ital b}} at room temperature are among the lowest that have been reported in the literature, indicatingmore » that our samples are of high quality. The ratio {rho}{sub {ital a}}/{rho}{sub {ital b}} is independent of temperature between 150 and 275 K, and its value, 2.2{plus minus}0.2, indicates that the Cu-O chains contribute 60% of the current when the electric field is parallel to them, with the rest of the current being contributed by the Cu-O planes. This result, at zero frequency, is in good agreement with the recent conductivity at infrared frequencies obtained by Schlesinger {ital et} {ital al}.« less