Chemical etching of silicon assisted by graphene oxide under negative electric bias

Chemical etching of silicon assisted by graphene oxide (GO) is attracting attention as a new method to fabricate micro- or nano- structures. GO promotes the reduction of an oxidant, and holes are injected into silicon, resulting in the preferential dissolution of the silicon under GO. We developed a new etching method that applies a negative bias to the silicon substrate. The silicon under GO was more selectively etched in an etchant consisting of hydrofluoric acid and nitric acid. We assume that this is attributed to the difference in hole concentration in the silicon under GO and in the bare silicon. In addition, the in-plane diffusion of holes in silicon is suppressed by this method, resulting in forming highly anisotropic pores. We combined this etching method with microcontact printing (μCP) of GO, showing its potential for silicon microfabrication.