Profile analysis of thin film X-ray diffraction peaks

In this study, we have analysed the X-ray diffraction peak profiles of thin films using the two main models usually applied to bulk materials: the integral width and the Warren-Averbach method, in thin films, the structure is nanocrystalline leading to diffraction peak profiles very different from those found in the bulk. Consequently, the application of the usual deconvolution models sometimes gives erroneous results, such as negative microdistortions or coherently diffracting domains sizes. This is probably due to the hypothesis underlying the models or/and to the difficulties to perform a good profile Fourier transform due to a poorly defined background. The case of gold, platinum and tungsten thin films are considered. The microdistortions are very important (up to 5 X 10(-3)) compared with those of a heavily cord worked bulk materials (10(-3)) and the size of their coherently diffracting domains is nanometric (2-20 nm). The discussion of these results suggests some new directions for research in this area.