The Origin of Mo₂C Films for Surface-Enhanced Raman Scattering Analysis: Electromagnetic or Chemical Enhancement?

Abstract

The relatively weak Raman enhanced factors of semiconductor-based substrate limit its further application in surface-enhanced Raman scattering (SERS). Here, a kind of two-dimensional (2D) semimetal material, molybdenum carbide (Mo2C) film, is prepared via a chemical vapor deposition (CVD) method, and the origin of SERS is investigated for the first time. The detection limits of the prepared Mo2C films for crystal violet (CV) and rhodamine 6G (R6G) molecules are low at 10–6 M and 10–8 M, respectively. Our detailed theoretical analysis, based on density functional theory and the finite element method, demonstrates that the enhancement of the 2D Mo2C film is indeed CM in nature rather than the EM effects. Besides, the basic doping strategies are proposed to further optimize the SERS sensitivity of Mo2C for Fermi level regulation. We believe this work will provide a helpful guide for developing a highly sensitive semimetal SERS substrate.