Accuracy of energy dispersive x-ray composition analysis of YBCO films on yttrium-containing substrates as compared to Rutherford backscattering spectroscopy

We address the accuracy of Energy Dispersive X-ray Spectroscopy (EDS) compo sition analysis of YBa2Cu3O7-x (YBCO) thin films. YBCO films deposited on y ttrium stabilized zirconia (YSZ) and strontium titanate (STO) substrates we re analyzed by EDS and Rutherford Backscattering Spectrometry (RBS) to dete rmine their compositions. The YSZ substrates used in this work contained a common element, yttrium; therefore, EDS intensities of yttrium signals resu lting from the film alone were calculated using EDS results of blank YSZ su bstrates. The EDS compositions of all the elements were obtained using the proportionality factor, k calculated from RBS data from a standard film dep osited on silicon and the intensity ratios of the respective standard obtai ned from EDS. The film thickness was found to be an important factor to con sider when choosing the optimum accelerating voltage for the EDS analysis. For films having comparable thickness to that of the standard (similar to 0 .8 mu m), we found 25 kV was the optimum accelerating voltage for the EDS a nalysis that obtained compositions in good agreement with the RBS data. For films having half the thickness of the standard film, EDS composition anal yses were unreliable quantitatively and were best qualitatively at 15 kV. ( C) 2000 Kluwer Academic Publishers.