We report on pulsed laser deposition of YBa2Cu3O7−x in a diluted O2/Ar gas resulting in thin epitaxial films which are almost outgrowth-free. Films were deposited on SrTiO3 or MgO substrates around 800 °C at a total chamber pressure of 1.0 mbar, varying the argon partial pressure from 0 to 0.6 mbar. The density of boulders and outgrowths usual for laser deposited films varies strongly with Ar pressure: the outgrowth density is reduced from 1.4×107 to 4.5×105 cm−2 with increasing Ar partial pressure, maintaining a critical temperature Tc,zero≊90 K and a transport critical current density Jc(77 K)≥106 A/cm2 by extended oxygenation time during cool down.
YBa2Cu307-x (mco) thin films with superconducting transition temperatures above 91 K were deposited on both sides of double-sided, polished LaAIOa(lOO) substrates. Using ex situ furnace annealing, the substrates could be kept at 45% during the codeposition of Y, Cu and BaF2. No O2 was necessaty in the deposition chamber. The furnace annealing was carried out in a mixture of Ar, O2 and H20 vapour. The gas flow was 1000 sccm at an O2 partial pressure of 1.0 mbar. The maximum annealing temperature was 810°C which was maintained for 1 h. Double-sided YBCO superconducting thin films may provide a good base material for microwave devices in which one superconducting side acts as a low-loss ground plane.
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