Electronic Structure and Band Gap Engineering of Two-Dimensional Octagon-Nitrogene

TL;DR

This study predicts and analyzes the electronic properties of a newly proposed 2D octagon-structured nitrogen, demonstrating its stability and tunable large band gap for potential electronic applications.

Contribution

It introduces a new 2D nitrogen phase, octa-nitrogene, and explores its stability, electronic structure, and band gap engineering via strain and electric field.

Findings

ON is dynamically stable with no imaginary phonon modes.

Single-layer ON is a large-gap semiconductor with a 4.7 eV band gap.

Strain and electric field can induce an insulator-to-metal transition.

Abstract

We have predicted a new phase of nitrogen with octagon structure in our previous study, which we referred to as octa-nitrogene (ON). In this work, we make further investigation on its electronic structure. The phonon band structure has no imaginary phonon modes, which indicates that ON is dynamically stable. Using ab initio molecular dynamic simulations, the structure is found to stable up to 100K, and ripples that are similar to that of graphene is formed on the ON sheet. Based on DFT calculation on its band structure, single layer ON is a 2D large-gap semiconductor with a band gap of 4.7eV. Because of inter-layer interaction, stackings can decrease the band gap. Biaxial tensile strain and perpendicular electric field can greatly influence the band structure of ON, in which the gap decreases and eventually closes as the biaxial tensile strain or the perpendicular electric field increases. In other words, both biaxial tensile strain and perpendicular electric field can drive the insulator-to-metal transition, and thus can be used to engineer the band gap of ON. From our results, ON has potential applications in the electronics, semiconductors, optics and spintronics, and so on.