Sketch and Peel Focused Ion Beam Patterning of Black Phosphorus for Mid-Infrared Photonics

Abstract

Black phosphorus (BP) is an important mid-infrared semiconductor, having a direct bandgap from monolayer (≈1.7 eV) to bulk (≈0.31 eV) thicknesses. The ability to nanopattern BP could enable new optoelectronic devices. However, existing nanopatterning techniques are either limited to thin flakes or produce BP with poor optical properties. Here, focused neon ion beam lithography is used to produce functional BP nanostructures. We demonstrate a “sketch and peel” method. The “sketch” step removes BP in a narrow line that outlines the desired structure. In the “peel” step, a hardened polymer droplet is used as a handle to pull off the surrounding flake. The “sketch and peel” method minimizes the ..