State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou, P. R. China.
School of Environment and Chemical Engineering, Foshan University, Foshan, P. R. China.
Sci Rep. 2018 Jan 26;8(1):1674. doi: 10.1038/s41598-018-19496-7.
A new phase of nitrogen with octagon structure has been predicted in our previous study, which we referred to as octagon-nitrogene (ON). In this work, we make further investigations of its stability and electronic structures. The phonon dispersion has no imaginary phonon modes, which indicates that ON is dynamically stable. Using ab initio molecular dynamic simulations, this structure is found to be stable up to room temperature and possibly higher, and ripples that are similar to that of graphene are formed on the ON sheet. Based on the density functional theory calculation, we find that single layer ON is a two-dimension wide gap semiconductor with an indirect band gap of 4.7 eV. This gap can be decreased by stacking due to the interlayer interactions. 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 a 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, we see that ON has potential applications in many fields, including electronics, semiconductors, optics and spintronics.
在我们之前的研究中，已经预测到具有八边形结构的氮的新阶段，我们称之为八边形氮（ON）。在这项工作中，我们进一步研究了其稳定性和电子结构。声子色散没有虚声子模式，这表明 ON 是动力学稳定的。通过第一性原理分子动力学模拟，发现该结构在室温及可能更高温度下稳定，并且在 ON 片上形成类似于石墨烯的波纹。基于密度泛函理论计算，我们发现单层 ON 是一种二维宽带隙半导体，其间接带隙为 4.7eV。由于层间相互作用，堆叠可以减小这个间隙。双轴拉伸应变和垂直电场可以极大地影响 ON 的能带结构，其中随着双轴拉伸应变或垂直电场的增加，带隙减小，最终关闭。换句话说，双轴拉伸应变和垂直电场都可以驱动绝缘到金属的转变，因此可以用来工程化 ON 的带隙。从我们的结果来看，我们看到 ON 在电子学、半导体、光学和自旋电子学等许多领域都有潜在的应用。
