中文摘要：

采用密度泛函理论方法,对Cs以不同覆盖度吸附在石墨烯表面时系统的结构稳定性和场发射性能进行了研究。计算结果表明单原子Cs吸附在石墨烯表面的碳六元环的中心位置时系统的能量最低。随着Cs的覆盖度增加,碱金属Cs与石墨烯之间的吸附作用逐渐增强,（4×4）R 0°和（2×2）R 0°结构是稳定的。由于碱金属Cs的修饰作用,Cs/石墨烯体系的功函明显下降,且随着碱金属Cs的覆盖度增大,系统的功函逐渐减小。态密度的计算结果表明功函的下降主要与Cs和石墨烯之间的电子转移有关。随着覆盖度的增大,石墨烯的电子态逐渐向低能方向移动,系统的费米能级升高并导致材料的功函下降。

英文摘要：

Relying on the density functional theory（DFT）, the structural stability and field emission performance of Cs/graphene compound with different Cs coverage were investigated. The results indicated that the adsorption of single Cs atom on the center site of hexatomic ring is energetically favorable. With the increase of Cs coverage,the adsorption interaction between Cs and graphene are gradually enhanced,（4 ×4）R 0° and（2×2）R 0° structures are stable. Due to the modification effect of Cs metals, the work function of Cs/graphene system decreases obviously, and it is continuously reduced with increasing of Cs coverage. The computational results of the density of states（DOSs） identified that the reduction of the work function is mainly related to the electron transfer between Cs and graphene. With increasing of Cs coverage, the electronic states will shift to a lower energy position, leading to the increase of Fermi energy and the reduction of work function.