Formation of Hierarchical Nanoparticle Pattern Arrays Using Colloidal Lithography and Two-Step Self-Assembly: Microspheres atop Nanospheres

Abstract

We report a simple approach to the fabrication of hierarchical nanoparticle arrays and film patterns using a novel combination of colloidal lithography (CL), two-step self-assembly, and reactive-ion etching (RIE). In this approach, a uniform nanoparticle film (∼15−50 nm particle diameter) is first deposited on a substrate. Then, larger (several hundred to thousands of nanometers diameter) microparticles with a different composition are self-assembled into well-ordered patterns atop the nanoparticle film. Next, reactive-ion etching is used to remove parts of the initial nanoparticle film using the upper layer of large particles as a mask. After selective removal of the remaining upper layer of large particles, hierarchical nanoparticle patterns are obtained on flat surfaces. Hexagonal patterns of small nanoparticle film arrays were easily fabricated with a monolayer of large spheres using this approach. Moreover, the shape and diameter of nanoparticle film disks depend on the etching duration while the per...