Solid-solid interface reconstruction at equilibrated Ni-Al ₂O ₃ interfaces

The atomistic structure of solid Ni-Al ₂O ₃ interfaces at equilibrium was determined by aberration-corrected transmission electron microscopy, from specimens formed during solid-state dewetting of thin Ni films on the (0 0 0 1) surface of α-Al ₂O ₃. It was found that the interface develops a unique mechanism for misfit strain reduction, termed delocalized coherency, via a 2.53×2.53R30 reconstructed interface structure, contradicting most simulations in the literature, which assume a semi-coherent structure for this system. Based on the experimental work presented here, a structural model was also simulated, showing periodic buckling of the terminating Ni layer (i.e. interface reconstruction). The interface energy was experimentally determined from dewetted Ni particles using Winterbottom analysis, and found to be 2.16 ± 0.2 J m ^-2 at P(O ₂) = 10 ^-20 atm and T = 1623 K.