Monolayer black phosphorus by sequential wet-chemical surface oxidation

TL;DR

This paper introduces a simple chemical method to produce monolayer black phosphorus flakes with controlled thickness, using layer-by-layer oxidation and passivation techniques to preserve electronic properties for device fabrication.

Contribution

It presents a novel wet-chemical oxidation process for thinning black phosphorus to monolayers and demonstrates effective passivation methods to prevent further oxidation.

Findings

Successful fabrication of monolayer black phosphorus flakes

Effective passivation techniques to prevent photooxidation

Preservation of electronic properties in BP FETs

Abstract

We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent. Moreover, the oxidation process can be stopped at will by two different passivation procedures, namely the non-covalent functionalization with perylene diimide chromophores, which prevents the photooxidation, or by using a protective ionic liquid layer. The obtained flakes preserve their electronic properties as demonstrated by fabricating a BP field-effect transistor (FET). This work paves the way for the preparation of BP devices with controlled thickness