Rashba spin splitting and photocatalytic properties of GeC-MSSe (M = Mo, W) van der Waals heterostructures

Vertical stacking of ultrathin two-dimensional materials via weak van der Waals (vdW) interactions is identified as an important technique for tuning the physical properties and designing viable products for nanoelectronics, spintronics, and renewable energy source applications. The geometry, electronic, and photocatalytic properties of vdW heterostructures of GeC and Janus transition metal dichalcogenides MSSe (M = Mo, W) monolayers are investigated by performing first-principles calculations. Two different possible models of GeC-MSSe heterostructures are presented with an alternative order of chalcogen atoms at opposite surfaces in MSSe. The most favorable stacking pattern of both models is dynamically and energetically feasible. A direct type-II band alignment is obtained in both models of understudy heterobilayer systems. The spin orbit coupling (SOC) effect causes considerable Rashba spin splitting in both MSSe monolayers. In particular, a greater Rashba spin polarization is demonstrated in model 1 (GeC-WSSe) than model 2 (GeC-MoSSe) caused by the alternative order of chalcogen atoms and larger SOC effect of heavier W than Mo atoms, which provides a platform for experimental and theoretical understanding of designing two-dimensional spintronic devices. More interestingly, the appropriate band alignments of model 1 with the standard water redox potentials enable its capability to dissociate water into H+/H-2 and O-2/H2O. In contrast to model 1, model 2 can only oxidize water into O-2/H2O. The simulated design of GeC-MSSe is predicted for promising use in future electronic, spintronics, and photocatalytic water splitting.