Anisotropic infrared absorption in monolayer black phosphorus metasurface with/without local oxidative effect*

As one kind of anisotropic two-dimensional (2-D) layered material, the monolayer black phosphorus (BP) has ability to excite the surface plasmon resonance in the infrared spectrum, thus providing sufficient conditions for the strong light-matter interaction, so that some potential applications can be shown in the field of optoelectronics. Based on those physical properties, we design the patterned monolayer BP to achieve extremely high infrared absorption, and meanwhile use the finite element method to model the effects of factors such as n-type doping concentration, dielectric thickness, and angle of incidence light. Moreover, due to the strong anisotropic in-plane properties of monolayer BP, we analyze detailedly the absorption spectra in both the armchair and zigzag directions separately, and then understand that low-angle narrow-band absorption in the zigzag direction could be captured in that structure. The structure could achieve perfect absorption in the zigzag direction at an incidence angle of 89.3 degrees with n-type doping concentration n = 3 x 1013 cm-2 and medium thickness d = 4.6 mu m, and the maximum absorption can reach 99.98% with the full width at half peak (FWHM) of only 0.57 mu m. Considering the case on surface oxidation, it may occur some possible effects for the perfect absorption, but with our structure, the proposed narrow-band absorption still have wide applications in the sensing and light body monitoring.

Automated summary

Monolayer black phosphorus has the ability to excite infrared absorption, making it useful in optoelectronics. By designing patterned monolayer black phosphorus, we have achieved high infrared absorption, which is significant for various applications.