Analysis of grain orientation and intergrain properties by micro-Raman spectroscopy in YBa₂Cu₃O_7−x thin films

Abstract

Superconducting YBa 2 Cu 3 O 7−x (YBCO) thin films grown by pulser-laser-assisted deposition were studied by micro-Raman spectroscopy. This technique was used to estimate the epitaxial quality of the films in terms of the presence of c-axis-and a-axis-oriented areas. The advantage of micro-Raman spectroscopy is its high lateral resolution, and this was used to study the homogeneity of the films at submicrometric level. Local structural changes from a large number of intergrain regions were revealed by changes of the Raman parameters. For example, the aggregation of a-axis-oriented grains formed needle-shaped macrograins. Micro-Raman measurements suggest that these grains were seeded at large-angle grain boundaries in c-axis-oriented areas.

Structural and superconducting properties of EuBa2Cu3O7 xthin films grown by off-axis pulsed laser deposition

“…Raman spectra may also be used for estimating the texture factor of the samples [24]. As the average intensity ratio m = I O(4)-Ag /I O(2,3)-B1g has been reported [25] to correlate with the percentage of a-axis oriented grains, we should mainly observe the O(2, 3)-B 1g mode for c-axis oriented films. Raman spectra, obtained on different regions of the films Eu123-2 and Eu123-3, show orientational inhomogeneity which can be essentially associated to a-axis oriented areas.…”