Variations of the elemental composition distribution over the thickness of YBa2Cu3O7-δ thin films obtained by pulsed laser deposition from one target

Abstract

Epitaxial YBa₂Cu₃O_7‒δ (YBCO) films 150–200 and 300 nm thick, respectively, were deposited on SrTiO₃ (100) substrates by pulsed laser deposition at different conditions: with and without using the velocity filtration technique. The films have T(R = 0) in the range of 77.4–87 R(T) depending on the conditions of deposition from one target with YBa₂Cu₃O_6.8 composition. The films contain Zn, Sr, Pd, Ag and Ti impurity elements obtained from the target (a total of no more than 2 at. %). Data of the film resistance temperature dependences, X-ray phase analysis, analysis of X-ray fluorescence (XRF) spectra and study of the surface relief by SEM methods revealed the nonuniform distributions of impurity and matrix Y, Ba, Cu elements over the film depth. Impurity concentrations near the surface lead to the formation of faceted spiral pyramids on the surface, which probably evolve into large elongated particles according to the Ostwald mechanism. This knowledge is practically important for optimizing pulsed laser deposition technologies and creating 2D instruments and devices for studying physical phenomena.