Total pattern fitting for the combined size-strain-stress-texture determination in thin film diffraction
A global approach has been developed to analyze complex thin film structures by X-ray diffraction. The method is based on the fitting of multiple data, diffraction pattern and/or images, collected at different orientation of the sample to obtain all the information needed. It requires the knowledge of the crystal structure for the phases present in the film, or if the amount/film thickness is sufficient, the crystal structure can be also determined or refined. Reflectivity patterns can be added to the global refinement to improve the accuracy of the thickness determination and when coupled with total X-ray fluorescence can give the in depth chemical concentrations. In addition, it constraints the solution for the quantitative phase analysis obtained from the diffraction patterns. The principles of the analysis with the main methods will be presented from the theoretical point of view. These cover the models from crystal structure to texture, residual strain/stresses, crystallite sizes and microstrains. To make the method more effective, some specific models have been developed in the past few years. Then some experimental/analysis examples will be given to enlighten how the method works and what kind of information can be obtained. Not every model suits every analysis or kind of thin film and the examples will cover different cases from multiple phases to strong texture, epitaxial thin films or multilayers.