Influence of thermal annealing and of the substrate on sputter-deposited thin films from EUROFER97 on tungsten

•Sputter-deposited films from EUROFER97 on tungsten were thermal annealed.•In-situ measurements using ion beam analysis were performed to monitor modifications.•Change of microstructure, segregation of W, and reaction with substrate were observed.•No tungsten-rich regions were observed on the film annealed on a MgO substrate.•Results highlight the impact of tungsten in the modification of deposited materials.