Observation of thickness dependent anomalous spin filtration in MoS2 ultra-thin films

Abstract

This study exposes novel spin filtering phenomena in ultra-thin MoS2 films deposited on indium tin oxide (ITO) substrates. The novelty lies in the explicit dependence of spin polarization and filtering efficiency on the film thickness. MoS2, a transition metal dichalcogenide, exhibits promising spintronic properties due to its intrinsic spin–orbit coupling and the potential to control spin orientation. We prepared MoS2 films of various thicknesses on ITO substrates and investigated their spin-filtering behavior using scanning tunneling spectroscopy (STS). Results reveal that the degree of spin polarization is highly sensitive to the MoS2 layer thickness, with ultra-thin films (4 nm) exhibiting reverse spin polarization compared to thicker films (10–15 nm). This spin flipping is attributed to the structural deformations in MoS2 thin films, such as twisting and folding, that break spatial symmetry and induce chirality. These chiral distortions modulate the electronic states and promote spin-selective transport in the crystal. The findings underscore the tunability of spin filtering in MoS2/ITO structures through geometric control, offering valuable insights for developing chirality-assisted spintronic devices.