CONTROL OF YBCO SHEET RESISTANCE WITH NI IMPLANTATION

It was found that the resistance of YBa2Cu3O7-x (YBCO) films could be well controlled by Ni ion implantation. Both resistance and susceptibi lity measurements showed that the critical temperature (T-c) of a film was systematically suppressed from its original value to an insulting state with increasing implantation dose. The sheet resistance varies from 6 Omega/square to >20 Omega/square at 77 K with dose ranging from 1 x 10(13) to 2 x 10(16) cm(-2). For doses above 1 x 10(16) cm(-2), w e observed an ion gettering effect after subsequent annealing in which the implanted ions diffuse against the concentration gradient and get ter towards the peak concentration region.