Generating Multiscale Gold Nanostructures on Glass without Sidewall Deposits Using Minimal Dry Etching Steps.

The advent of recent technologies in the nanoscience arena require new and improved methods for the fabrication of multiscale features (e.g., from micro- to nanometer scales). Specifically, biological applications generally demand the use of transparent substrates to allow for the optical monitoring of processes of interest in cells and other biological materials. While wet etching methods commonly fail to produce essential nanometer scale features, plasma-based dry etching can produce features down to tens of nanometers. However, dry etching methods routinely require extreme conditions and extra steps to obtain features without residual materials such as sidewall deposits (veils). This work presents the development of a gold etching process with gases that are commonly used to etch glass. Our method can etch gold films using reactive ion etching (RIE) at room temperature and mild pressure in a trifluoromethane (CHF3)/oxygen (O2) environment, producing features down to 50 nm. Aspect ratios of two are obtainable in one single step and without sidewall veils by controlling the oxygen present during the RIE process. This method generates surfaces completely flat and ready for the deposition of other materials. The gold features that were produced by this method exhibited high conductivity when carbon nanotubes were deposited on top of patterned features (gold nanoelectrodes), hence demonstrating an electrically functional gold after the dry etching process. The production of gold nano features on glass substrates open the possibility for the use of these biocompatible, high conductive and chemically stable materials in biological/biomedical applications.