FILM THICKNESS DEPENDENCE OF CRITICAL CURRENT-DENSITY FOR YBA2CU3O7 FILMS POSTANNEALED AT A LOW OXYGEN PARTIAL-PRESSURE

The variation of critical current density at 77 K as a function of film thickness was studied for YBa2Cu3O7 films on (100) LaAlO3 substrates. Film thicknesses were in the range 0.2-1.6 mum. The films were deposited by co-evaporation and post-annealed under conditions which have previously resulted in high-quality films (750-degrees-C and an oxygen partial pressure of 29 Pa). The critical current density at 77 K exceeds 1 MA cm-2 for the thinner films, and decreases with increasing film thickness in excess of about 0.4 mum. The decrease is in rough agreement with a switch from c-axis to a-axis growth at about this critical thickness. A good anticorrelation was found between room temperature resistivity and critical current density at 77 K. The results are compared to those obtained before by post-annealing at 850-degrees-C in 1 atm of oxygen.