SMOOTH YBA2CU3O7-X THIN-FILMS PREPARED BY PULSED-LASER DEPOSITION IN O2 AR ATMOSPHERE/

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-degrees- C at a total chamber pressure of 1.0 mbar, varying the argon partial p ressure from 0 to 0.6 mbar. The density of boulders and outgrowths usu al for laser deposited films varies strongly with Ar pressure: the out growth density is reduced from 1.4 x 10(7) to 4.5 x 10(5) cm-2 with in creasing Ar partial pressure, maintaining a critical temperature T(c,z ero) almost-equal-to 90 K and a transport critical current density J(c )(77 K) greater-than-or-equal-to 10(6) A/cm2 by extended oxygenation t ime during cool down.