This article is cited in 8 papers

Superconductivity

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

V. D. Okunev^a, S. J. Lewandowski^b, T. A. D’yachenko^a, O. Abal'oshev^b, P. Gierłowski^b, V. A. Isaev<sup>b

a</sup> Galkin Donetsk Institute for Physics and Engineering, Donetsk
^b Institute of Physics, Polish Academy of Sciences, Warsaw, Poland

Abstract: 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$p$ $\Rightarrow$ 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.

Received: 19.01.2010
Accepted: 29.04.2010

 English version: Physics of the Solid State, 2011, 53:1, 13–22

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