Graphene-buffered modulation of contact properties in Co/PtSSe vertical heterocontacts for spinFET applications

Rashba spin–orbit coupling-induced spin–momentum locking is a key mechanism enabling the development of spin field-effect transistors (spinFETs) for fast and energy-efficient computing. Recent studies have demonstrated the presence of spin–momentum locking via the local Rashba effect in the two-dimensional (2D) semiconducting material PtSSe, making it a promising candidate for 2D spinFET design. However, forming a high-quality interface between bulk ferromagnetic metals and PtSSe remains challenging due to the emergence of metal-induced gap states (MIGSs), which are caused by dangling bonds at the contact interface. To address this issue and enhance contact performance, a graphene-buffered vertical heterostructure comprising Co and PtSSe was theoretically designed using first-principles density functional theory calculations. The results show that introducing a graphene interlayer effectively suppresses MIGSs and significantly lowers the Schottky barrier height (SBH) at the Co/PtSSe interface. Moreover, the variation in SBH under an applied out-of-plane electric field shows a steeper slope in the graphene-inserted heterostructure compared to the direct Co/PtSSe contact. This indicates better gate tunability. In addition, a significant change in the Rashba parameter is observed under the external electric field. This combined tunability of SBH and Rashba parameters under an applied electric field provides a promising route for achieving a low subthreshold swing and a high ON/OFF current ratio in spinFETs. The presence of the graphene interlayer also greatly improves the spin polarization at the contact interface. These results provide important guidance for the design and development of advanced spinFET devices.