“…A preliminary study [10] evidenced that this low toughness is connected to the strong confinement of the plastic deformation in front of the notch, which strongly limits the energy dissipation during crack initiation and propagation. It was also observed that crack growth in polycrystalline thin films is usually intercrystalline [2,10]. This second observation, consistent with previous reports in the literature [11,12,13,14,15], suggests that grain boundaries (GBs) are easy crack propagation paths, as expected from the lower energy required to produce surfaces compared with an intracrystalline crack [16].…”