Effect of TCNQ layer cover on oxidation dynamics of black phosphorus

TL;DR

This study investigates how a TCNQ layer affects the oxidation process of black phosphorus, revealing that the TCNQ layer modifies oxidation dynamics and creates confined chemical environments.

Contribution

It demonstrates that a TCNQ layer alters oxidation behavior of black phosphorus and introduces a new method to study localized chemical processes on 2D materials.

Findings

TCNQ forms a fragmented, thin layer on black phosphorus.

Oxidation dynamics are significantly different under the TCNQ layer.

Confined spaces between TCNQ fragments influence chemical reactions.

Abstract

The puckered surface of black phosphorus represents an ideal substrate for an unconventional arrangement of physisorbed species and the resulting specific two-dimensional chemistry of this system. This opens the way to investigate the chemical and physical properties of locally confined areas of black phosphorus without the necessity for further physical downscaling of the material. We have evaporated TCNQ on top of black phosphorus under over-saturation non-equilibrium conditions in vacuum. The evolution of linear density and height of droplets formed through oxidation during exposure to air was studied time-dependently by scanning-force microscopy. Our study suggests that the TCNQ molecules spontaneously arrange in a thin layer of the order of a few nm height, which, however, is fragmented with a periodicity of about 100 nm. It is shown that within the confined space separating the layer fragments the chemical dynamics of the oxidation process is remarkably different than on a bare black phosphorus surface.