DOPANT INCORPORATION AND ANISOTROPY IN INPLANE ALIGNED A-AXIS ORIENTED YBA2CU2.78CO0.22O7-DELTA THIN-FILMS

We studied the effects of Co doping on the intrinsic anisotropic prope rties of in-plane aligned a-axis YBa2Cu3-xCoxO7-delta (x = 0.22) films , pulsed laser deposited on (100) LaSrGaO4 substrates. We used X-ray-a bsorption fine structure analysis and resistivity data to determine th e quality of Co incorporation. The introduction of Co-dopant is believ ed to cause O disorder which leads to CuO chain fragmentation. Higher deposition pressures provided films with better Co incorporation but s maller grain size. However, at lower pressures proper Co incorporation can still be achieved by slowing down the post-deposition cooling rat e. For transport along the c-direction, Co dopant causes an increase i n resistive anisotropy (rho(c)/rho(b)) with increasing level of O orde ring. Co doping level of x = 0.22 effectively doubles the resistive an isotropy of YBa2Cu3O7-delta films (from similar to 18 to similar to 40 at 100 K). (C) 1997 Elsevier Science B.V.