Structural and Opto electronic Study of 2D Black Phosphorus

Abstract

Two-dimensional black phosphorus (BP), having broad tunability in its direct bandgap and highest carrier mobility in single-layer con guration among all semiconducting two-dimensional (2D) layered materials, has attracted tremendous attention towards the development of high speed electronic and opto-electronic devices.[1 3] The lay- ered BP shows a wide bandgap variation from visible to near infra-red (NIR) region, which varies from 0.3 eV (in bulk con guration) to 2.0 eV (in single layer con gu- ration). The bandgap of BP falls within the semiconducting range of 2D materials family, lling the gap between Graphene [zero bandgap] and transition metal di- chalcogenides (TMDCs) [absorption in the visible range].[2, 4 6] Reports suggest the superiority of BP based eld-e ect-transistors (FETs) over TMDCs, exhibit- 2 and#8722;1 and#8722;1 ing very high hole mobility ( and#956; e gt1000 cm V s ), large on-set current (I on and#956; A / and#956; m) and#8764; 300 8 and the large on-o ratio (I on / I o gt10 ).[7 9] However, the behavior of lay- ered BP under external perturbations like mechanical stress, optical exposure, and electrostatic eld is still unexplored, which are very crucial factors to extend its application in nano-electronic devices under harsh conditions. This thesis, entitled Structural and Opto-electronic Study of 2D Black Phosphorus: A Perspective from Raman Spectroscopy , provides a route to understand and monitor the key physical properties of BP for possible applications in opto-electronics and sensing. In order to understand the structural stability of layered BP ake, High-Pressure Ra- man spectroscopy of a few-layer BP ake has been carried out. The extensive study of Raman spectra under applied pressure con rms the structural stability of BP ake for mechanically harsh conditions as high as and#8764; 4.2 and#8764; 5.9 GPa. At applied pressure of GPa, an orthorhombic to a rhombohedral phase transition has been observed, which is simultaneously reversible and partial. The phase transition pressure has been identi ed experimentally from the abrupt change in blueshif