Band alignment of monolayer MoS2/4H-SiC heterojunction via first-principles calculations and x-ray photoelectron spectroscopy

Abstract

2D/3D heterostructures have received extensive attention due to their unique structures and outstanding properties. In this work, the structural and electronic properties of monolayer MoS2/4H-SiC(Si-face) heterojunctions are systematically investigated through density functional theory calculation and experimental analysis. The calculated results show that the monolayer MoS2/4H-SiC heterostructure is a van der Waals heterojunction because of low formation energy and shows a type-II band alignment with a valence band offset of 1.43 eV. Then the type-II band alignment of the MoS2/4H-SiC heterostructure is verified by x-ray photoelectron spectroscopy. However, there is a deviation of 0.44 eV in the valence band offset between the calculated results and the experimental data, which may be caused by the underestimation of the bandgap by the Perdew–Burke–Ernzerhof method and the introduction of impurities at the interface. Our experimental results reveal the type of band alignment and the combination of the MoS2/4H-SiC heterostructure interface, which is an effective way to understand and design photocatalysts and electronic devices.

Interface Structure and Doping of Chemical Vapor Deposition‐Grown MoS2 on 4H–SiC by Microscopic Analyses and Ab Initio Calculations

“…The simplest model of a MoS 2 /4H–SiC(0001) heterostructure can be constructed through the direct interaction of this ideal surface with a single‐layer MoS 2 sheet, resulting in minimum energy arrangement where sulfur atoms of the MoS 2 layer relax on top of the Si surface atoms, in agreement with previous calculations. [ 20 ] Figure 4b shows the geometry of the relaxed interface, with a calculated SiS interface bond distance of 2.24 Å and an interface binding energy of 0.73 eV atom −1 . Both characteristics indicate a strong (covalent) MoS 2 –SiC interaction, which is not consistent with the experimental evidence of a vdW gap at the MoS 2 /4H–SiC(0001) interface (see Figure 1c).…”

“…Recently, ab initio computational studies of the equilibrium configurations for 1L–MoS 2 heterostructures with the Si‐terminated SiC(0001) surface have been reported, showing that the most energetically stable configuration is the one where S atoms are located on top of Si atoms with an equilibrium distance d Si–S = 2.21 Å. [ 20 ] Such a small d Si–S value indicates a strong (covalent‐like) bond between MoS 2 and 4H–SiC(0001) in this idealized model of the heterostructure. In this context, further computational studies considering additional effects, such as the natural propensity of the Si‐terminated 4H–SiC surface to be passivated by oxygen atoms, are required to provide a more realistic description of the 1L–MoS 2 /4H–SiC system.…”