Nanoepitaxy of anatase-type TiO₂ on CeO₂ nanocubes self-assembled on a si substrate for fabricating well-aligned nanoscale heterogeneous interfaces

Nanoscale epitaxy or nanoepitaxy for fabricating macroscopically well-aligned nanoscale heterogeneous interfaces on a Si substrate is demonstrated, combining bottom-up and top-down processes efficiently. TiO ₂ sputtered in vacuum was selectively nucleated on the atomically flat surfaces of individual CeO₂ nanocubes prefabricated by self-assembly in solution on the substrate, and anatase-type TiO₂ was grown after a heat treatment by solid-phase epitaxy to produce tandem nanocrystals with heterogeneous interfaces. The atomic configurations of the tandem nanocrystals fabricated after sputtering and subsequent annealing were determined using high-resolution scanning transmission electron microscopy to characterize the nanoscale heterogeneous interfaces. Sharp heterogeneous interfaces were observed between the anatase TiO₂(001) and the CeO₂(001) nanocubes, with the TiO₂ [110] directions being parallel to the CeO₂ [100] directions. This unique nanoepitaxial growth technique will contribute to the development of devices and catalytic materials incorporating functional tandem nanocrystals with nanoscale heterogeneous interfaces.