Convergent ion beam alteration of 2D materials and metal-2D interfaces

Abstract

Abstract Tailoring the properties of two-dimensional (2D) crystals is important for both understanding the material behavior and exploring new functionality. Here we demonstrate the alteration of MoS 2 and metal-MoS 2 interfaces using a convergent ion beam. Different beam energies, from 60 eV to 600 eV, are shown to have distinct effects on the optical and electrical properties of MoS 2 . Defects and deformations created across different layers were investigated, revealing an unanticipated improvement in the Raman peak intensity of multilayer MoS 2 when exposed to a 60 eV Ar + ion beam, and attenuation of the MoS 2 Raman peaks with a 200 eV ion beam. Using cross-sectional scanning transmission electron microscopy (STEM), alteration of the crystal structure after a 600 eV ion beam bombardment was observed, including generated defects and voids in the crystal. We show that the 60 eV ion beam yields improvement in the metal-MoS 2 interface by decreasing the contact resistance from 17.5 kΩ · µ m to 6 kΩ · µ m at a carrier concentration of n 2D = 5.4 × 10 12 cm −2 . These results advance the use of low-energy ion beams to modify 2D materials and interfaces for tuning and improving performance in applications of sensors, transistors, optoelectronics, and so forth.