石墨烯红外波段复折射率及消光性能研究

Complex refractive index and extinction performance of graphene in infrared bands

石墨烯是一种新型二维纳米碳材料,在红外干扰方面具有很大的潜在应用价值,其红外消光特性值得深入研究。文中利用红外椭偏仪测量了石墨烯压片在红外波段的椭偏参数,计算得到其红外波段的复折射率,采用离散偶极近似(DDA)方法计算了石墨烯在2~14μm波段的效率因子、消光系数与入射波长、粒子直径和厚度的关系。计算结果表明,石墨烯在2~14μm波段具有优异的红外消光性能,其消光性能主要取决于材料的吸收性能,吸收作用大于散射作用,同时粒子对近、中红外辐射的消光性能明显好于远红外波段;消光效率因子和消光系数随波长增加逐渐减小;消光效率因子随粒子直径的增加而增大,近、中红外波段的消光系数大于远红外波段,其中直径0.25~1μm粒子的消光系数最大,直径1~4μm粒子的消光系数随直径增加逐渐减小,直径大于4μm的粒子对各波段红外的消光能力受粒度变化的影响很小;消光效率因子随粒子片层厚度的增加逐渐增大,近、中红外波段的消光系数随厚度的增加有所减小,而远红外波段的消光系数受粒子厚度变化影响不大。

As a new type of two-dimensional nano-carbon material, graphene has great potential application value in infrared interference, and its infrared extinction characteristics are worthy of in-depth study. In this paper,the ellipsometric parameters of graphene pellet in the infrared bands were measured by infrared ellipsometry, and the complex refractive index was calculated. Subsequent, the relationships between efficiency factors, extinction coefficient and the incident wavelength, diameter, thickness in 2-14 μm wavebands of graphene particles were calculated with discrete dipole approximation(DDA) method. Results show that graphene has excellent infrared extinction performances in 2-14 μm wavebands, and the extinction performance of the particles to near-infrared and mid-infrared radiation is better than that of far-infrared band. The extinction performances mainly depend on the absorption properties of the particles, and the absorption is better than the scattering effect. The extinction efficiency factor and extinction coefficient gradually decrease with the increase of wavelength. The extinction efficiency factor increases with the increase of the particle’s diameter. The extinction coefficient in near-infrared and middle-infrared bands is better than that in far-infrared bands, of which the particles with diameter of 0.25-1 μm have the largest extinction coefficient. The extinction coefficient of the particles with diameter of 1-4 μm decreases slowly with the increase of diameter, while the extinction ability of particles with diameter larger than 4 μm is little affected by the change of particle size. The extinction efficiency factor gradually increases with the increase of the thickness of graphene sheet, the extinction coefficient in near-infrared and middle-infrared bands decreases with the increase of the thickness, while the extinction coefficient in far-infrared bands is less affected by the change of particle thickness.