Ordered Nano-Crystal Arrays Spontaneously Form in Films Evaporated onto Nanopore Array Substrates

TL;DR

This study demonstrates that thin films of Pb and Sn evaporated onto nanopore substrates spontaneously form ordered nano-crystal arrays aligned with the substrate's hole pattern, driven by surface energy effects.

Contribution

It reveals the conditions under which nano-crystal arrays form on nanopatterned substrates, highlighting the role of surface energies and material wetting properties.

Findings

Pb and Sn films form ordered arrays aligned with nanopore patterns.

Surface energies influence the self-assembly process.

Materials that wet the substrate do not form arrays.

Abstract

We present SEM images of films thermally evaporated onto Anodic Aluminum Oxide substrates that are patterned with a hexagonal array of 34 and 80 nm diameter holes spaced by 100 nm. Over a range of film thicknesses, Pb and Sn films spontaneously self assemble into an array of nano-crystals in registry with the underlying hole lattice. The development of the arrays with thickness indicates that surface energies drive coalescing grains to move over the holes. Materials that wet the substrate or whose grains do not coalesce at these substrate temperatures do not form arrays. We discuss some potential applications.