Microstructure Characterization of Multilayer Thin Coatings ZrN/Si3N4 by X-Ray Diffraction Using Noncoplanar Measurement Geometry

The structural characterization of multilayer thin coatings is performed by X-ray diffraction using a noncoplanar measurement geometry. The application of such a measurement geometry enables a reliable and comprehensive microstructural analysis of the material comparing to other measurement geometries due to the accessibility to a larger number of measured Bragg reflections. The important advantage of noncoplanar geometry is a measurement setup without tilting and rotating the sample. A set of profiles for different Bragg reflections is measured for several multilayer coatings with different thicknesses of individual layers; the obtained profiles are combined into a single scan for the simultaneous fittingby a theoretical curve. The broadening of the diffraction profiles is considered to be affected by a small grain size and instrumental effects, with the grains being modeled by ellipsoidal shape with two equal in-plane axes. Based on the proposed fitting procedure, the microstructural parameters of multilayer coatings are evaluated, including the grains size in parallel and normal to the surface directions. The dependence of evaluated grains size on the measurement direction confirms the validity of the selected grains model. The microstructural parameters evaluated from noncoplanar X-ray diffraction show a good agreement with those obtained from HRTEM and STEM techniques.