ON THE ROLE OF AG IN IMPROVED YBA2CU3O7.DELTA FILMS

In the present paper, we report that (i) silver could also help in cry stallization along the c-direction, as shown in high quality Ag-doped YBa2Cu3O7-delta (YBCO) films prepared by both laser ablation and DC Ma gnetron sputtering. in the case of the c-oriented films on (100) SrTiO 3 and (100) LaAlO3 substrates in the near surface region, from ion cha nneling analysis, we obtained chi(min)=1.5% and chi(min)=3.5%, respect ively better than the undoped films; (ii) some Ag was found to re-evap orate during the film deposition and the percentage of retained As was dependent on the deposition techniques (mainly the deposition time an d temperature). By RES and ion channeling analyses we have found that about 1 wt.% Ag remained in the laser ablated Ag-doped film prepared f rom a 3 wt.% Ag-YBCO target, and (iii) at least some retained Ag occup ied substitution positions. Jc (77K) measured by the SQUID magnetomete r for the laser ablated Ag-doped film was found to be enhanced by a fa ctor of 2 in comparison with the undoped film. The Jc enhancement in A g doped films may not totally come from the improvement of the in-plan e alignment.