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 c 0 decreased. However, at D longer than 50 mm, the values of T c and c 0 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≥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 YBa2Cu3O z target.