Unraveling thickness-dependent structural properties of CrSBr nanoflakes using hyperspectral TERS imaging

CrSBr, a layered van der Waals material with intrinsic air stability and layer-dependent magnetic and electronic properties, has emerged as a promising 2D semiconductor. However, nanoscale insight into its thickness-dependent structural and electronic behavior remains limited. In this study, we employ hyperspectral tip-enhanced Raman spectroscopy (TERS) imaging to investigate the vibrational and electronic properties of exfoliated CrSBr nanoflakes. Both confocal Raman and TERS measurements reveal a systematic enhancement of the A 2 g Raman mode relative to the A 3 g mode in thinner flakes. The I(A 2 g )/I(A 3 g ) intensity ratio decreases consistently with increasing flake thickness, reflecting underlying changes in the electronic band structure. Hyperspectral TERS mapping confirms this trend at the single-flake level and suggests a resonance Raman enhancement influenced by electron–phonon coupling near the band edge. Our results establish the I(A 2 g )/I(A 3 g ) ratio as a sensitive spectroscopic marker for thickness-dependent band structure evolution in CrSBr. More broadly, this work highlights hyperspectral TERS as a powerful tool for probing local structure–property relationships in emerging low-dimensional materials.