**3. Results**

The Results section is structured in two parts. In this first part, in situ annealing experiments on the fiber textured Al0.73Sc0.27N/Mo(110)/AlN(0001)/Si(001) (sample set #1) thin films are discussed with respect to intrinsic and extrinsic effects of observed anomalous thermal expansion. In the second part, the effect size of the thermal expansion behavior and the microstructural changes to epitaxial thin film samples of Al1−xSc*x*N/Al2O3(0001) are analyzed depending on Sc concentration (0 < *x* < 0.40) (sample set #2). Structural data recorded before and after annealing are discussed and data recorded during annealing will be compared. Eventually, we conclude on our hypotheses considering data from sample #3.
