Figure 3. Pre- and post-annealing structures of the W and HEA films after 3 days at 1,100 °C.

The top surfaces, cross-sections and grain structures indicate significant grain coarsening, pore formation and morphology change in tungsten films upon annealing, but the difference of microstructure and strengths of the HEA films before and after annealing is minor under the same deposition and annealing conditions. Scale bars, 200 nm (the first column, large magnifications of top surfaces); 300 nm (the last column, EBSD maps); 1 μm (the other images).