INFLUENCE OF SPUTTERING CONDITIONS ON THE CHARACTERISTICS OF SUPERCONDUCTING Y-BA-CU-O FILMS

Influences of the substrate holder bias voltage V(H), the oxygen partial pressure P(O2), and the distance D between the substrate and the target on the superconducting characteristics of Y-Ba-Cu-O thin films were investigated. The optimum bias voltages were from -10 V to -20 V for total gas pressure P = 300-500 mTorr. With increasing distance at P = 500 mTorr, the critical temperature T(c) increased and the c-lattice parameter co decreased. However, at D longer than 50 mm, the values of T(c) and c0 did not depend on D. These films have the maximum T(c) of 90 K and the c-lattice parameter ranging from 1.167 to 1.169 nm. These results imply that the sputtering conditions of P(O2) greater-than-or-equal-to 300 mTorr, V(H) of -10 V to -20 V and D>5 cm at 500 mTorr are necessary for fabricating the films having T(c) of 87-90 K by means of on-axis rf magnetron sputtering having a YBa2Cu3Oz target.