High quality YBa2Cu3O7-δ/PrBa2Cu3O7-δ multilayers grown by pulsed injection MOCVD

YBa2Cu3O7-delta/PrBa2Cu3O7-delta multilayers have been grown with the new technique pulsed injection MOCVD. Micro-droplets of a solution containing a mixture of organometallic beta-diketonates (Y : Pa : Cu or Pr : Pa : Cu), dissolved in an appropriate solvent were sequentially injected, to stack thin layers of YBa2Cu3O7-delta and PrBa2Cu3O7-delta. Dilution and droplet volume were optimized to decrease the growth rate of each compounds and to increase the precision of films thickness control. Superlattices, deposited on LaAlO3 substrate, with different period thickness (from 331 to 67 Angstrom) were elaborated and characterized with SEM, X-ray diffraction and AC-susceptibility measurement. Results indicate a broadening of X-ray reflections and a decreasing of twinning angle with decreasing period. Superconducting measurement shows that for a YBa2Cu3O7-delta thickness superior to 175 Angstrom, multilayer have YBCO bulk properties. When the thickness is less than 175 Angstrom the influence of the isolating barrier is evidenced. (C) 2000 Elsevier Science B.V. All rights reserved.