Fabrication of Ag Dot Arrays Using Reusable Porous Alumina Masks

Abstract

Ag dot arrays with uniform sizes are functional materials with a wide range of applications, such as substrates for surface-enhanced Raman scattering (SERS) and catalyst nuclei for the formation of semiconductor wires by vapor–liquid–solid (VLS) growth. In this study, we fabricated a reusable porous alumina mask (PAM) to establish a method for the efficient preparation of ordered arrays of Ag dots with uniform sizes. To form an array of Ag dots on a substrate using PAM, the PAM must be thin. However, because thin PAMs are fragile, they lack the mechanical durability required for handling as freestanding films. To address this issue, we fabricated a PAM supported by an Al framework. By placing the resulting PAM in contact with a substrate and depositing Ag, Ag dots of uniform size were formed at positions corresponding to the through holes in the PAM. Although Ag was also deposited on the PAM surface during thermal deposition, it could be selectively dissolved by etching with an aqueous nitric acid solution. Consequently, we were able to repeatedly form arrays of Ag dots of uniform size on a substrate using the same PAM. The Ag dot arrays obtained using this method were also demonstrated to be useful as substrates for the highly sensitive SERS detection of a model molecule.