Electronic structure, optical and photocatalytic performance of SiC–MX₂ (M = Mo, W and X = S, Se) van der Waals heterostructures

The stacking of monolayers in the form of van der Waals heterostructures is a useful strategy for band gap engineering and the control of dynamics of excitons for potential nano-electronic devices. We performed first-principles calculations to investigate the structural, electronic, optical and photocatalytic properties of the SiC-MX₂ (M = Mo, W and X = S, Se) van der Waals heterostructures. The stability of most favorable stacking is confirmed by calculating the binding energy and phonon spectrum. SiC-MoS₂ is found to be a direct band gap type-II semiconducting heterostructure. Moderate in-plane tensile strain is used to achieve a direct band gap with type-II alignment in the SiC-WS₂, SiC-MoSe₂ and SiC-WSe₂ heterostructures. A difference in the ionization potential of the corresponding monolayers and interlayer charge transfer further confirmed the type-II band alignment in these heterostructures. Furthermore, the optical behaviour is investigated by calculation of the absorption spectra in terms of ε₂(ω) of the heterostructures and the corresponding monolayers. The photocatalytic response shows that the SiC-Mo(W)S₂ heterostructures can oxidize H₂O to O₂. An enhanced photocatalytic performance with respect to the parent monolayers makes the SiC-Mo(W)Se₂ heterostructures promising candidates for water splitting.