Electron Beam as Straightener to De-Wrinkle Large 2D Black Phosphorus Flake: An In Situ TEM Monitoring

Large area 2D nanomaterials are susceptible to the formation of surface corrugations during synthesis, transfer, and handling of samples and their physicochemical properties are extraordinarily affected by the formation of surface corrugations. Even though several strategies have been devised by researchers for smoothing the 2D flakes, the issue is far from resolved. Here, the straightening of black phosphorus (BP) flakes using electron beam irradiation that enables the removal of ripples, disclination, and line defects from lattice are reported. The crystallinity and buckling of the flake are controlled by varying the electron fluence rate and irradiation time in a high-resolution transmission electron microscopy set-up. Experimental results show that the optimal electron beam exposure (20 to 30 min of exposure at fluence rate = 1.02 x 10(29) m(-2) s(-1)) de-stresses/relaxes the lattice and the maximum ordering of lattice planes is achieved; beyond which, the stress in lattice rises again and lattice planes start buckling. Thus, straightening the 2D flakes using an electron beam ensures the removal of surface corrugations with nanoscale precision and allows for real-time monitoring of the process.