EFFECT OF DIFFERENT OXIDIZING GASES ON THE INSITU GROWTH OF YBA2CU3O7-DELTA FILMS BY PULSED LASER DEPOSITION

The effectiveness of oxygen (O2), nitrous oxide (N2O), and nitrogen dioxide (NO2) as oxidizing agents during in-situ growth of YBa2Cu3O7-delta (YBCO) films on (100) SrTiO3 substrates by pulsed laser deposition has been studied as a function of deposition temperature (700-800-degrees-C), and laser wavelength ( 1 93, 248 and 355 nm), for a wide range of oxidizer gas pressure (0.1-200 mTorr). In general, the superconducting transition temperature of the films has been found to increase with increasing oxidant pressure, with zero-resistance temperature approximately 90 K only obtained in films prepared in a relatively high pressure (150-200 mTorr) of oxidizer ps. At lower pressures, the transition temperature while being depressed is quite sensitive to the nature of the oxidant, the laser wavelength and the deposition temperature. Nevertheless, independent of the oxygen source or other growth parameters, an almost linear decrease in transition temperature with a corresponding increase in the c-axis lattice parameter has been observed for all the film. YBCO films have also been deposited in a low pressure background (less-than-or-equal-to 1 mTorr) using a combination of atomic oxygen and pulsed molecular oxygen. The results are discussed in terms of the oxygen requirement for kinetic and thermodynamic stability of YBCO during growth of the film by pulsed laser deposition.