銅ナノ薄膜の疲労き裂進展特性に及ぼす表面酸化層の影響

抄録

To investigate the effects of surface oxide layer on fatigue crack propagation properties, fatigue crack propagation experiments were conducted on approximately 500-nm-thick freestanding copper (Cu) films without surface oxide layer and compared with the properties of the films with roughly 1-nm-thick surface oxide layer. Just before the fatigue crack propagation experiment in a field emission scanning electron microscope (FESEM), surface oxide layer on one side of the specimen was etched by argon ion sputtering. In situ FESEM observations of fatigue crack propagation confirmed that intrusions/extrusions were formed ahead of the fatigue crack tip, and the fatigue crack then propagated preferentially through these intrusions/extrusions in the region of the stress intensity factor range ΔK ≲ 4 MPam^1/2. In the region of ΔK ≳ 4 MPam^1/2, the fatigue crack propagated in tensile fracture mode. These mechanisms of fatigue crack propagation were similar to that in the films with surface oxide layer. The relationships between fatigue crack propagation rate (da/dN) and ΔK showed no significant effects of surface oxide layer in ΔK ≲ 4MPam^1/2.