Polycrystalline Au Nanomembrane as a Tool for Two-Tone Micro/Nanolithography

A Au nanomembrane is utilized as a hydroxyl ion channel to develop negative and positive-tone micro/nanolithography. Less than 50 nm thick Au films, that is, Au nanomembranes, have nanopores through which ions can pass. Micro- and nanostructures can be fabricated by using an Au nanomembrane-deposited Al layer with KOH solution loading on it. Hydroxyl ions diffuse over Au nanomembranes to react with an underneath Al layer. Depending on the pH of the fabrication process, which is governed by the volume of KOH solution loaded onto an Au nanomembrane-deposited Al layer, protruded aluminum hydroxide structures (positive tone lithography) or micro/nanotunnels (negative tone lithography) are able to be obtained. A flexible THz photonic structure and microfluidic channels have been demonstrated as possible applications of these structures.