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

Abstract

originating from the nonuniform interlayer spacing of a wrinkled 2D structure leads to alteration in band structure and eventually restricts from attaining ideal experimental conditions. [15][16][17] Due to the atomically thin dimension, it is practically impossible to polish out the irregularities by physical or chemical means, as standardized in conventional silicon process flow. Quite a few efforts were made to develop post-synthesis process for minimizing surface corrugations on 2D crystal, however, most of the strategies were made for pre-transfer and post-transfer processes during drytransfer of 2D flakes. [8,[18][19][20][21][22][23][24] Pre-transfer techniques are optimized by the hydrophobic substrate, transfer media, and environment (vacuum or inert atmosphere) conditions so as to prevent the formation of wrinkles during the transfer of nanolayers. [25][26][27][28][29][30] Even though the microscale management of surface corrugations is possible using pre-transfer techniques, nanoscale surface irregularities invariably creep in during the transfer process. Post-transfer techniques like plasma treatment, high-temperature annealing, isotropic stretching, and mechanical cleaning are thus used for the removal of surface irregularities after the transfer of flakes. Currently, available post-transfer techniques are not without limitations and plasma treatments, as well as hightemperature annealing tends to introduce defects in 2D crystals. Furthermore, nanomaterials with high chemical reactivity (e.g., 2D black phosphorus (BP)) are incompatible with these processes. [27,[30][31][32][33][34][35][36][37][38] Mechanical cleaning approaches such as contact mode atomic force microscope (AFM) have also been tried by researchers for removal of surface corrugations but have their own limitations with respect to multilayers, speed, and introduction of defects by the scanning tip. [21,[38][39][40][41][42][43] Overall, the prevalent techniques leave a lot to be desired when it comes to the controlled removal of surface corrugations without the introduction of defects in 2D crystals. It is thus imperative to develop and explore innovative approaches in which smoothness/relief of 2D flakes is precisely controlled while maintaining the pristine crystallinity.Electron beam can introduce defects in 2D lattices as well as improve the conductivity of 2D layers but the de-wrinkling of 2D flakes using e-beam has not been investigated by researchers. [44] In this context, we introduce e-beam based 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 ...

Recent Advances in Low‐Dimensional Nanomaterials for Photodetectors

“…Kaur et al demonstrated a straightening method to smoothen and de-wrinkle of 2D BP flakes via electron beam irradiation to improve crystallinity and remove line defects from the lattice. [143] The ironing of BP using electron beam irradiation enabled to control the stress in lattice and the buckling structure of the flake, which can be an important moving forward for controlling 2D atomic nanostructure. Another novel way to enhance optoelectronic properties for PD applications is using hybrid heterostructures.…”