Abstract
The oxidation ability of various oxidants for Bi2Sr2CaCuOx and related cuprates were evaluated both by experiments and by a thermodynamical calculation. When Bi2Sr2CaCu2Ox sputtered films were treated at 400°C with such oxidants as photo-activated O2, NO2, O3, and N2O, significant Tc change was observed. This Tc change was found in parallel with the variation of c-lattice parameter and verified to originate from oxygen nonstoichiometry in the films by the Hall coefficient measurement. The highly oxidative property of NO2, ozone, and atomic oxygen derived from this experiment was supported by the thermodynamical calculation for the oxidation of Cu2O to CuO. The results were further utilized to grow alkaline earth cuprate films by pulsed laser deposition in ultrahigh vacuum (laser MBE). In situ RHEED and XPS analyses clearly indicated that alkaline earth cuprates could be grown epitaxially and laterally under such conditions as 700°C and 1×10-7 NO2pressure.
