SURFACE DEGRADATION OF SUPERCONDUCTING YBA2CU3O7-DELTA THIN-FILMS

The surface degradation of c-axis oriented YBa2Cu3O7-delta thin films due to air, CO2, N2, O2, and vacuum exposure has been studied with ref lection high-energy electron diffraction (RHEED), scanning tunneling m icroscopy, and contact resistivity measurements. The formation of an a morphous surface reaction layer upon exposure to air and CO2 is monito red with RHEED and correlated with an increase in contact resistivity. The contact resistivity of samples exposed to air increases with time t as rho(c) = (1.0 x 10(-7) OMEGA cm2)e(square-root t/64 min). Surfac es exposed to CO2 show a similar degradation while surfaces exposed to N2 showed a slightly different degradation mechanism. Vacuum exposed surfaces how little increase in contact resistivity, indicating no lon g-term surface oxygen loss.