Blistering in Helium-Ion-Irradiated Zirconium, Aluminum, and Chromium Nitride Films

Abstract

This work is devoted to studying blistering in ZrN, AlN, and CrN films formed by reactive magnetron sputtering. The surface morphology and cross-sectional microstructure of mononitride films after irradiation with He ions (energy 40 keV and doses of 3 × 1017−1.1 × 1018 cm–2) at room temperature are analyzed by scanning, atomic force, and transmission electron microscopy. The critical doses of blistering are determined for ZrN (6 × 1017 cm–2), AlN (5 × 1017 cm–2), and CrN (6 × 1017 cm–2) films. The high density of blisters in ZrN films leads to the merging of neighboring blisters (average size 0.75 μm) and the formation of large blisters (average size 1.35 μm). The blisters in the AlN films have a regular round shape (average size 1.7 μm). The СrN films are characterized by the presence of open blisters having a two-level structure: an upper blister with a diameter of 2−10 μm and a lower one with a diameter of 1.2 μm. As follows from the TEM results, 40‑keV He-ion irradiation of the films and their subsequent vacuum annealing leads to the formation of chains of radiation-induced pores filled with helium in the region of the projective ion range Rp. The formation of extended cracks is found to occur in the Rp region of ZrN, which is caused by interbubble fracturing due to high excess pressure in pores located at a depth close to Rp.