Transformation from an atomically stepped NiO thin film to a nanotape structure: A kinetic study using x-ray diffraction

Transformation from an atomically stepped epitaxial thin film of NiO to a self-assemble nanotape structure at the step edge was observed in situ using synchrotron x-ray diffraction. The pristine NiO thin film was epitaxially grown on an ultrasmooth sapphire (0001) substrate with a regular step of 0.2 nm in height using laser molecular beam epitaxy. Transformation from the thin film to the nanotape structure was facilitated by postannealing in air from room temperature to 620 K . From the Arrhenius plot of ln(in-plane domain sizes) versus 1 ∕ T , an atomic-scale transformation energy of ∼ 0.0135 eV /atom was derived.