Nanoscale Morphology, Defect Identification and Electronic Spectroscopy of Thin Molybdenum Carbide (α-Mo₂C) Crystals under Ambient Conditions

The emerging materials family of thin transition metal carbides (TMCs) have garnered significant recent attention due to their distinctive features such as high thermal and chemical resistance, good electrical and thermal conductivity, high hardness, and potential for energy storage as well as electromagnetic shielding. The application potential of thin TMCs will strongly depend on atomic-scale structural and physical-chemical properties. On the other hand, the necessity of high vacuum and low temperatures for atomic-resolution experiments has led to a debate regarding the relevance of such characterization approaches for real-life applications.<br/><br/>Here, we present a nanometer- and atomic-scale characterization study of thin crystals of molybdenum carbide (α-Mo₂C) grown through chemical vapor deposition (CVD). The experiments are performed via conductive atomic force microscopy (C-AFM), under ambient conditions. It is found that the crystal surfaces are partially covered by graphene. Moreover, atomic-resolution imaging, combined with density functional theory (DFT), allows the identification of various defects found on the crystal surfaces. Finally, current vs. voltage spectroscopy performed on the defects provides information about their local influence on surface electronics.