Surface energy guided sub-10 nm hierarchy structures fabrication by direct e-beam etching

Abstract

It is found that surface energy plays the dominant role in direct e-beam etching of single crystal ZnO and ITO nanostructures through a surface etching (sputtering) process, especially for electron energies smaller than the characteristic energy for bulk atoms knock-off. This mechanism can be used for the fabrication of sub-10 nm hierarchical structures on single crystal nanostructure precursors. We performed detailed in situ HRTEM observations of the surface energy guided etching (SEGE) process on ZnO nanowires. The etching of (0001) crystal planes, that have the lowest surface energy, was found to dominate the etching process. It is also shown that the SEGE mechanisms can be extended to single crystal ITO nanowires for sub-10 nm hierarchical structure fabrication. The hierarchical structures fabricated by the SEGE process show increased specific surface areas (SSA), which may be useful in fields such as sensors, catalysts and solar cells.