Understanding the Physics and Chemistry of 2D Materials’ Oxidation Process

by | Jun 21, 2017

While the electronic and structural properties of 2D materials make them appealing, their chemical stability—especially in ambient conditions—is not favorable.

Two dimensional (2D) materials have stimulated considerable scientific activities worldwide due to their exceptional properties and promising applications in electronics and optoelectronics. Notable, recently discovered 2D materials include group IV elemental monolayers silicene and germanene, group V elemental monolayer phosphorene, and binary monolayers such as hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2).

While the electronic and structural properties of these materials make them appealing, their chemical stability—especially in ambient conditions—is not favorable. Because oxidation fundamentally changes the electronic structure (and therefore the nature of the materials), its effect in general needs to be understood both for advancing our fundamental understanding and its impact on the material’s technological applications.

In the review article “Physics and chemistry of oxidation of two-dimensional nanomaterials by molecular oxygen” recently published in WIREs Computational Molecular Science, Ravindra Pandey and colleagues from Michigan Technological University and the US Army Research Laboratory discuss recent experimental and theoretical studies on the oxidation of 2D materials. They focus on the relationship between the oxidation process and the energy values, which can be calculated by first-principles methods. Generally, the energy values of interest are cohesive energy, energy barrier to oxidation and dissociation energy of oxygen molecule on 2D materials. The combination of experimental and theoretical results reveals a significant role of the structure, chemical bonds and native defects in 2D materials for their practical applications in devices at a nanoscale.

Despite the great promises of 2D materials, challenges are still present in scaled-up, high purity synthesis/growth, characterization, and integration of these materials into nanoscale devices. Effective passivation or encapsulation methods need to be developed for 2D materials such as silicene, germanene, and phosphorene, which are very promising for high-speed electronics, optoelectronics, and sensor applications. Unfortunately these are chemically unstable in the presence of oxygen. Experimental and theoretical studies would facilitate the industrialisation of 2D materials for the next-generation of devices.

Text contributed by the authors.