Monolayer black phosphorus by sequential wet-chemical surface oxidation

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Black phosphorus (BP) is a promising 2D material with unique electronic properties.
• Controlling the thickness of BP flakes, especially down to the monolayer, is crucial for optimizing device performance.
• Existing methods for thinning BP can be complex or may degrade its electronic characteristics.

Purpose of the Study:

• To develop a straightforward chemical methodology for precise thickness control of black phosphorus flakes.
• To achieve BP flakes down to the monolayer limit.
• To demonstrate that the thinning process preserves the intrinsic electronic properties of BP.

Main Methods:

• Employed layer-by-layer oxidation and thinning of black phosphorus flakes.
• Utilized water as a solubilizing agent during the oxidation process.
• Implemented two passivation strategies to halt oxidation: non-covalent functionalization with perylene diimide chromophores and application of a protective ionic liquid layer.

Main Results:

• Successfully controlled the thickness of black phosphorus flakes down to the monolayer.
• Demonstrated effective passivation of photooxidation using perylene diimide functionalization and ionic liquid layers.
• Fabricated a black phosphorus field-effect transistor (BP FET) using the thinned flakes, confirming the preservation of electronic properties.

Conclusions:

• A facile chemical method for controlled thinning of black phosphorus to monolayer thickness has been established.
• The developed passivation techniques effectively protect black phosphorus from degradation.
• This approach enables the preparation of black phosphorus devices with precisely controlled thickness and preserved electronic functionality.