Disordering of the electronic structure of YBaCuO amorphous films upon incorporation of crystalline clusters formed in laser-induced plasma into their composition

The effect of crystalline clusters formed in a laser-induced plasma on the optical properties of YBa 2 Cu 3 O 6 + x amorphous films prepared by pulsed laser deposition has been investigated. It has been demonstrated that an increase in the number of clusters leads to a gradual disappearance of interference fringes inherent in optically homogeneous media. Simultaneously, the incorporation of metallic and insulating clusters into the amorphous medium results in a decrease in the optical band gap E 0 of the YBaCuO amorphous matrix from 1.28 to 1.06 eV and a considerable decrease in the probability of interband optical transitions with charge transfer O 2 p → Cu 3 d due to the loosening of the structure and generation of local stresses. It has been revealed that there is an additional band gap E 1 , which decreases from 0.25–0.30 eV to zero values with a decrease in the optical band gap E 0 . The additional gap has been interpreted as an energy gap between localized states that belong to the valence and conduction bands. A decrease in the density of electronic states in the narrow 3 d band leads to the overlap of tails of the density of states, so that the band gap E 1 becomes negative.