Nano-Raman Spectroscopy Figure of Merit and Chemical Analysis of Contaminations in Single-Layer MoSe₂

Contaminations in the formation of two-dimensional heterostructures can hinder or generate the desired properties. Recent advancements have highlighted the potential of tip-enhanced Raman spectroscopy (TERS) for studying materials in the 2D semiconductor class. In this work, we investigate the influence of 50-200 nm sized nanoprotuberances within a monolayer of MoSe₂ using nano-Raman spectroscopy, establishing correlations between the presence of localized contaminations and the observed hyperspectral variations. A figure of merit is established for the identification of surface impurities, based on the MoSe₂ peaks ratio resulting from TERS field coherence. New spectral peaks are also identified, which are associated with the presence of nanoprotuberances and indicate contamination and oxidation with localized charge transfer between MoSe₂ and contaminant species.