scientists at the agency for science, technology and research (a*star) in singapore have demonstrated that phosphorene, a two-dimensional material, can be stabilized with the right choice of substrate and an electrical field, which could advance the production of flexible, low-power electronic devices.

the absorption of oxygen (red) damages phosphorene (purple, top), but the phosphorene is protected when on a molybdenum diselenide substrate (bottom).
(a*star institute of high performance computing)

according to a report from a*star, phosphorene is a semiconducting 2-d material that is useful in electronics, but it oxidizes in air and its quality degrades rapidly.

using first-principles calculations, a team of researchers showed that by placing phosphorene on a molybdenum diselenide substrate and applying a vertical electrical field, the oxidation of the phosphorene layer would be significantly reduced.

“the fast oxidation of freestanding phosphorene in ambient conditions is due to a low energy barrier for oxygen absorption of about 0.57 electronvolts: oxidation can occur in less than a minute,” the article explained.

“when this analysis is repeated with phosphorene overlying molybdenum diselenide, the energy barrier is much higher,” it continued. “as well, the model shows that the presence of the molybdenum diselenide substrate enables more effective tuning of the properties of the phosphorene with an electric field. this increases the oxidation energy barrier even further.”

with a vertical electrical field, researchers increased the energy barrier to 0.91 electronvolts and increased the lifetime of the phosphorene by a factor of five.

the research was recently published in nanoscale. the abstract stated:

“currently, a major hurdle preventing phosphorene from various electronic applications is its rapid oxidation under ambient conditions. thus, how to enhance its chemical stability by suppressing oxidation becomes an urgent task.

“here, we reveal a highly effective procedure to suppress the oxidation of phosphorene by employing a suitable van der waals (vdw) substrate and a vertical electric field. our first-principles study shows that the phosphorene-mose₂ vdw heterostructure is able to reverse the stability of physisorption and chemisorption of molecular o₂ on phosphorene.

“with further application of a vertical electric field of −0.6 v å⁻¹, the energy barrier for oxidation is able to further increase to 0.91 ev, leading to a 10⁵ times enhancement in its lifetime compared with that without using the procedure at room temperature.

“our work presents a viable strategy to vastly enhance the chemical stability of phosphorene in air.”