MECHANISMS FOR THE PERSISTENT PHOTOCONDUCTIVITY OF OXYGEN-DEFICIENT YBA2CU3O6+X

The mechanism for the persistent photoconductivity of oxygen deficient YBa2Cu3O6+x films is proposed. Photoexcited electrons fill vacant ele ctron orbitals of O- in the Cu-O-... chains. Photoexcited holes remain free and cause an increase in the density of mobile holes in CuO2 pla nes. To recombine with holes the electrons have to overcome an barrier of approximately 1 eV, corresponding the excitation energy from the l ocalized levels in the chains into the upper conduction band. Proposed model of a photoinduced charge transfer is consistent with available experimental data.