PERMANENT PHOTOINDUCED CHANGES IN THE TRANSPORT-PROPERTIES OF BI2SR2CACU2O8-FILMS(DELTA THIN)

We have observed permanent photoinduced decreases in both normal-state conductivity and T-c for Bi2Sr2CaCu2O8+delta epitaxial thin films. Th ese changes which are induced by illuminating the films with high-powe r-density He-Ne laser light are opposite to and substantially smaller than the case of persistent photoconductivity in oxygen-deficient YBa2 Cu3Ogamma. Moreover, no relaxation is observed even at room temperatur e. However, a characteristic time for the changes of a few tens of hou rs and insensitivity to illumination with infrared light are similar t o the case of YBa2Cu3Ogamma. These similarities, as well as the substa ntial dependence of the T-c decrease on post-annealing conditions for these films, strongly suggest that these photoinduced phenomena are ca used by a displacement of oxygen atoms in the Bi-O double layers.