Oxygen Control in Bi2Sr2Ca1Cu2Ox Superconducting Thin Films by Activated Oxygens

Abstract

Activated oxygens were generated by various methods to compare their effect on the control of oxygen stoichiometry in Bi₂Sr₂Ca₁Cu₂O _x superconducting thin films. The treatment of a film with an oxygen plasma or ozone at 400°C decreased the T _c onset of the film by as much as 20 K from untreated film as it was in the case of film treatment in atmospheric oxygen under UV light irradiation. On the other hand, films exposed to UV light irradiation in the presence of N₂O (400 Torr) increased their T _c onset to 100 K by about 20 K. These T _c changes accompanied the change in the c-axis lattice constant. The lattice of the specimens with T _c onset of 60 K was smaller than that of the untreated films, while the specimens with T _c onset of about 100 K had a stretched c-lattice. Thus, the oxygen content or hole concentration in Bi₂Sr₂Ca₁Cu₂O _x films can be controlled at a relatively low temperature and its effect is reflected in the changes of lattice constant and T _c.