Nanostructured Silicon Membranes for Control of Molecular Transport

Abstract

A membrane that allows selective transport of molecular species requires precise engineering on the nanoscale. Membrane permeability can be tuned by controlling the physical structure of the pores. Here, a combination of electron-beam and optical lithography, along with cryogenic deep reactive ion etching, has been used to fabricate silicon membranes that are physically robust, have uniform pore-sizes, and are directly integrated into a microfluidic network. Additional reductions in pore size were achieved using plasma enhanced chemical vapor deposition of silicon dioxide to coat membrane surfaces. Cross sectioning of the membranes using focused ion beam milling was used to determine the physical shape of the membrane pores before and after coating.