Few-layer MoS as nitrogen protective barrier.

We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS on graphene. Surface morphology of our MoS/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS layer is prevented by a very high vertical diffusion barrier, indicating that MoS can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.