F覆盖度对石墨烯体系电子结构和光学性能的影响

为了研究不同F覆盖度下石墨烯吸附体系的电子结构和光学性能,采用第一性原理对本征石墨烯和石墨烯吸附体系进行了几何优化,计算并分析了各体系的吸附能、能带结构、电子态密度、光吸收系数与反射率.结果表明,F原子稳定吸附在石墨烯的顶位,当F覆盖度为6.2%时,体系吸附能最大.F原子的吸附打开了石墨烯的能隙,使其由半金属型转变为半导体型.当F覆盖度为3.1%时,体系能隙值最大.与本征石墨烯相比,石墨烯吸附体系在费米能级处的电子态密度值增大,当F覆盖度为9.4%时,可以获得最大态密度值.石墨烯吸附体系的光吸收系数和反射率峰值相比本征石墨烯均明显减小,且F覆盖度越大,峰值减小程度越显著.在一定波长范围内吸附体系的吸收系数和反射率均出现蓝移现象.

Effect of F coverage on electronic structure and optical properties of graphene system

In order to study the electronic structure and optical properties of graphene adsorption system under different F coverage, the geometric optimization of intrinsic graphene and graphene adsorption system was carried out with the first principles, and the adsorption energy, band structures, the density of states, light absorption coefficient and reflectivity of each system were calculated and analyzed. The results show that F atoms are stably adsorbed on the top position of graphene. When the coverage of F atoms is 6.2%, the adsorption energy of the system reaches the maximum value. The adsorption of F atoms opens the band gap of graphene, which makes the grapheme change from the semi-metal type into the semiconductor type. When the coverage of F atoms is 3.1%, the band gap of the system reaches the maximum value. Compared with the intrinsic grapheme system, the graphene adsorption system increases the value of density of states at the Fermi level. When the coverage of F atoms is 9.4%, the maximum density of states can be obtained. Compared with the intrinsic grapheme system, the light absorption coefficient and reflectivity peaks of graphene adsorption system obviously reduce. In addition, the larger the coverage is, the more obvious the peaks decrease. The blue-shifted phenomenon of both light absorption coefficient and reflectivity appears within a certain range of wavelength.