A Raman measurement of cation disorder in YBa2Cu3O7-x thin films

X-ray diffraction (XRD) and Raman microscopy were used to probe cation diso rder within a series of epitaxial c-axis YBa2Cu3O7-x (YBCO) thin films grow n at different temperatures to give different c parameters. The Raman inten sity ratio (585)/(340) is found to correlate with X-ray intensity ratio (00 5)/(006) (which is known to measure cation disorder). The Raman method has the following advantages compared to the X-ray method: (1) local informatio n can be obtained with a spatial resolution of better than 1 mu m and (2) c hanges in oxygen content do not affect the Raman method. However, as the X- ray technique gives global measurements and as Raman is a near surface tech nique, the two techniques are complementary, We have also shown that cation disorder is inhomogeneous across a film surface and that this increases th e non-uniform strain within the material. (C) 2000 Elsevier Science B.V. Al l rights reserved.