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

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 (& epsilon; & AP; 0.03%) of 1L-MoS2, consistent with the small in-plane lattice mismatch, and a p-type doping of (0.45 & PLUSMN; 0.11) x 10(13) 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 d(Si-S )& AP; 3.84 & ANGS; bond length and p-type doping of MoS2; and 3) partial (1/4 ML and 1/2 ML) oxygen coverages of the 4H-SiC surface, resulting in intermediate values of d(Si-S) and doping behavior.