Fabrication of large area ordered metal nanoring arrays for nanoscale optical sensors

In contrast to metal nanodots, nanoring structures are accessible to various sensing and spectroscopy applications at nanometer scale due to their tunable plasmon resonances and large empty volume confined that provides more spaces for molecular attachment. In almost all the applications, fabrication of large area ordered metal nanoring arrays represents the first and one of the most significant challenges. This paper describes a simple and low-cost method of producing large area ordered metal nanoring arrays based on self-assembled monolayers of monodisperse colloidal spheres by combining reactive ion etching, sputtering and ion polishing techniques. Inner diameter, wall thickness and wall height of nanorings are controllable by varying the process conditions of reactive ion etching, sputtering, ion polishing or any combination thereof while their period can be changed by using colloidal spheres of various sizes. This new approach will surely facilitate further exploration of metal nanorings for applications in nanoscale optical sensors.