Fig. 4
From: Degradation of black phosphorus is contingent on UV–blue light exposure
a AFM micrograph on flakes that are initially exposed for only 10 min to 280 nm (UV) and 455 nm (blue), respectively. Subsequently, they are re-imaged after being stored in vacuum for 24 h. The control sample without exposure to UV or blue was left in a N2 environment in dark for the same duration to compare the degradation with the 10 min light-exposed flakes. The scale bars in a represent 1 µm. b Current decay with respect to exposure duration for the different wavelengths of light. It is seen that the relative degradation of current is the highest for flakes exposed to 280 nm (UV). c Micro-Raman spectra of BP flakes on SiO2/Si substrates after 60 min exposure to red, green, blue and UV respectively. The evolution of mixed POx and HxPOy signatures between 800 and 900 cm−1 can be observed for blue and UV exposures, whereas these features are absent for higher wavelengths. The corresponding extended range spectra is showm in Figure S1. d AFM images of a representative BP flake synthesised and stored under ambient conditions. e AFM image of a flake synthesised and stored in a standard photolithography lab that lacks UV light. A comparison of d, and e shows that the flake in a UV deficient environment remains intact, whereas the flake in ambient shows distinct signs of deterioration in 3 days. The scale bars in d, e represent 2 µm
