In situ Measurements of Irradiation-Induced Creep of Nanocrystalline Copper at Elevated Temperatures

We have measured irradiation-induced creep on nanocrystalline copper micropillars at elevated temperatures. The micropillars, which were ≈1 µm in diameter and ≈2 µm in height, were fabricated from magnetron-sputtered nanocrystalline copper films. The micropillars were compressed during 2.0 MeV Ar⁺ bombardment and the deformation measured in situ by laser interferometry. The creep rate was measured over the stress range 10–120 MPa at ≈200°C. The results show linear relationships of creep rate with both applied stress and displacement rate, yielding a creep compliance of 0.07 dpa⁻¹ GPa⁻¹ (dpa:displacement per atom). The findings are in good agreement with the previous results obtained using a bulge test on free-standing thin film specimens.