Plasma-assisted fabrication of monolayer phosphorene and its Raman characterization

There have been continuous efforts to seek for novel functional\ntwo-dimensional semiconductors with high performance for future applications in\nnanoelectronics and optoelectronics. In this work, we introduce a successful\nexperimental approach to fabricate monolayer phosphorene by mechanical cleavage\nand the following Ar+ plasma thinning process. The thickness of phosphorene is\nunambiguously determined by optical contrast combined with atomic force\nmicroscope (AFM). Raman spectroscopy is used to characterize the pristine and\nplasma-treated samples. The Raman frequency of A2g mode stiffens, and the\nintensity ratio of A2g to A1g modes shows monotonic discrete increase with the\ndecrease of phosphorene thickness down to monolayer. All those phenomena can be\nused to identify the thickness of this novel two-dimensional semiconductor\nefficiently. This work for monolayer phosphorene fabrication and thickness\ndetermination will facilitates the research of phosphorene.\n