Phase-and band-engineered MoS2-MoSe2 heterostructures via low-temperature plasma processing for molecular detection by charge-transfer-enhanced surface-enhanced Raman scattering

Surface-enhanced Raman spectroscopy (SERS) in chemically dominated enhancement systems depends critically on interfacial charge transfer (CT) between the substrate and the target analyte. The efficiency of this process is closely governed by the relative positions of the conduction and valence bands of the semiconductor substrate, making band structure engineering a critical factor in substrate design. In this work, we report the controlled fabrication of hybrid MoS 2 –MoSe 2 heterostructures with tunable 2H/1T phase ratios and S/Se ratios via plasma-assisted selenization and sulfurization at 400 °C, making them more compatible with back-end-of-line (BEOL) processes. The phase and defect structures of MoS 2 were first modulated by adjusting the sulfurization conditions of pre-formed MoOx thin films, thereby enabling vacancy-induced phase evolution. By tailoring the structural, compositional, and phase engineering, we effectively tuned the electronic band alignment to facilitate charge-transfer resonance with probe molecules. The resulting substrates demonstrated enhanced SERS activity toward Rhodamine B (RhB) and Crystal Violet (CV), achieving limits of detection down to 10 −8 M. This study highlights the importance of compositional and phase engineering in optimizing band structure for chemical-enhancement-driven SERS, and provides a low-temperature, scalable route for designing high-performance TMD-based Raman substrates.