Kumar Jeevesh, Shrivastava Mayank
Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore 560012, India.
ACS Omega. 2021 Feb 18;6(8):5619-5626. doi: 10.1021/acsomega.0c06058. eCollection 2021 Mar 2.
Lack of band gaps hinders application of graphene in the fields like logic, optoelectronics, and sensing despite its various extraordinary properties. In this work, we have done systematic investigations on direct band gap opening in graphene by hydrogenation and fluorination of carbon vacancies using the density functional theory computational approach. We have seen that although a carbon vacancy (void) opens an indirect band gap in graphene, it also creates unwanted mid gap (trap) states, which is attributed to unbound orbitals of the nearest unsaturated carbon atoms at the vacant site. The unsaturated carbon atoms and corresponding trap states can degrade the stability of graphene and create band gaps particularly for large size vacancies. We have proposed that hydrogenation or fluorination of the unsaturated carbon atoms near the vacant site helps in disappearance of the trap states while contributing to promising direct band gaps in graphene. The opened band gap is tunable in the infrared regime and persists for different sizes and densities of hydrogenated or fluorinated patterns. In addition, we have also found that the proposed approach is thermodynamically favorable as well as stable. This keeps the planar nature of the graphene monolayer, despite creation of defects and subsequent functionalization, thereby making it useful for 2D material-based electronics, optoelectronics, and sensing applications.
尽管石墨烯具有各种非凡特性，但缺乏带隙阻碍了其在逻辑、光电子和传感等领域的应用。在这项工作中，我们使用密度泛函理论计算方法，对通过碳空位的氢化和氟化在石墨烯中打开直接带隙进行了系统研究。我们发现，虽然碳空位（空洞）在石墨烯中打开了一个间接带隙，但它也产生了不需要的中间能隙（陷阱）态，这归因于空位处最近的不饱和碳原子的未结合轨道。不饱和碳原子和相应的陷阱态会降低石墨烯的稳定性，并产生带隙，特别是对于大尺寸空位。我们提出，空位附近不饱和碳原子的氢化或氟化有助于陷阱态的消失，同时在石墨烯中产生有前景的直接带隙。打开的带隙在红外区域是可调的，并且对于不同尺寸和密度的氢化或氟化图案都能持续存在。此外，我们还发现，所提出方法在热力学上是有利且稳定的。尽管会产生缺陷并随后进行功能化处理，但这保持了石墨烯单层的平面性质，从而使其可用于基于二维材料的电子、光电子和传感应用。
