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

Abstract

The interface structure and electronic properties of monolayer (1L) MoS2 domains grown by chemical vapor deposition on 4H–SiC(0001) are investigated by microscopic/spectroscopic analyses combined with ab initio calculations. The triangular domains are epitaxially oriented on the (0001) basal plane, with the presence of a van der Waals (vdW) gap between 1L–MoS2 and the SiC terraces. The high crystalline quality of the domains is confirmed by photoluminescence emission. Furthermore, a very low tensile strain (ε ≈ 0.03%) of 1L–MoS2, consistent with the small in-plane lattice mismatch, and a p-type doping of (0.45 ± 0.11) × 1013 cm−2, is evaluated by Raman mapping. Density functional theory (DFT) calculations of the MoS2/4H–SiC(0001) system are also performed, considering different levels of refinement of the model: 1) the simple case of the junction between Si-terminated SiC and MoS2, showing a covalent bond between the Si–S atoms and n-type doping of MoS2; 2) the complete passivation of Si dangling bonds with a monolayer (1 ML) of oxygen atoms, resulting in a vdW bond with dSi–S≈ 3.84 Å bond length and p-type doping of MoS2; and 3) partial (¼ ML and ½ ML) oxygen coverages of the 4H–SiC surface, resulting in intermediate values of dSi–S and doping behavior.