Ordering enhancement of nanoripples on Au/ARC bilayer by sequential ion bombardment: from a perspective of ripple superposition

As a promising nanofabrication tool, ion bombardment (IB) has attracted increasing attention because of its capability to induce quasi-periodic self-organized nanoripples. Continuous efforts have been made to improve the ordering of these IB-induced nanostructures and pursue experimental observations of IB-induced nanoripple superposition. This study experimentally demonstrates the feasibility of enhancing the ordering of ripples through the superposition of two sets of nanoripples on the surface of a Au/antireflection coating (ARC) bilayer using sequential IB (SIB). The atomic force microscopy data of the irradiated surface show that the ordering of the resulting nanoripples has been significantly improved along the directions parallel and perpendicular to that of the ripple vector, corresponding to a pronounced peak at a frequency of ∼0.01 nm^-1(i.e. a period of ∼100 nm) in the power spectral density curve and a long autocorrelation length (ACL) of ∼176 nm. In particular, the ACL of the ripples on the Au/ARC surface is approximately three times greater than that on the ARC surface. We demonstrate that the superimposition of nanoripples occurs during the bombarding of a Au/ARC bilayer system with a generalized SIB strategy. Furthermore, the basic requirements for the superposition of IB-induced nanoripples under non-conservation of mass are verified by extending the bombardment of bilayer systems from photoresist/ARC to Au/ARC. This study provides inspiration for academic research on the mechanism of ripple superposition and the application of ion beam technology in different fields.