Dopants induced structural and optical anomalies of anisotropic edges of black phosphorous thin films and crystals

A detailed experimental investigation of dopants modified black-phosphorus and methodology to deposit film on glass substrate have been conducted in order to improve the optical properties and wider utility. It was observed that Raman peaks were less intense for film, compared to separately grown black-P crystals. It was also observed that when synthesis duration was reduced to four hours, all Raman peaks became broader. A non-uniform material luminescence with dominance of green luminescence was observed when black-P crystals were irradiated with light of wavelength ~565–575 nm. The sulfur doped black-P illustrated fascinating rod-and-globule like deposits on the parent nano-coral black phosphorous substrate, whereas selenium doped black-P exhibits a localized concentration of Se in the near homogeneous phosphorous coverage. The boron and sulfur doping increased the band gap. In contrast, Se, In, and Ga doping resulted in a significant decrease in band gap energy. Frequency dependent dielectric functions of the anisotropic zig-zag and armchair edges of phosphorene suggest that doping of black –P causes a diminution in the first peak position for the zigzag electric field polarization demonstrating a gradual red shift. The red shift in the first peak position was perceived to be greatest for doping with boron exhibiting a band edge at 0.65 eV and least in the case of doping with sulfur, resulting in a band edge at 1.09 eV.