Figure 3.

(a) Polar representation of the absorption coefficient and experimental extinction spectra of the 40-nm intrinsic black phosphorus film. Absorption coefficient is represented with two different interband coupling strength β which gives different band gap value ω. Extinction spectra are obtained from FTIR spectroscopy with black phosphorus on SiO₂ substrate (Reproduced with permission of [49]. Copyright American Physical Society, 2014). (b) Hall mobility measured along x (armchair) and y (zigzag) direction on 8 nm and 15 nm black phosphorus film with constant hole doping concentration of 6.7 × 10¹² cm⁻². (c) Schematic of the device structure for determining the angle-dependent transport behavior and angular dependence of the drain current and the transconductance of a device. Device is composed of electrodes and black phosphorus film with 10 nm thickness (Reproduced with permission of [38]. Copyright American Chemical Society, 2014).