The interface of in-situ grown single-layer epitaxial MoS 2 on SrTiO 3 (001) and (111).

SrTiO(STO) is a versatile substrate with a high dielectric constant, which may be used in heterostructures with 2D materials, such as MoS, to induce interesting changes to the electronic structure. STO single crystal substrates have previously been shown to support the growth of well-defined epitaxial single-layer (SL) MoScrystals. The STO substrate is already known to renormalize the electronic bandgap of SL MoS, but the electronic nature of the interface and its dependence on epitaxy are still unclear. Herein, we have investigated anphysical vapor deposition (PVD) method, which could eliminate the need for ambient transfer between substrate preparation, subsequent MoSgrowth and surface characterization. Based on this, we then investigate the structure and epitaxial alignment of pristine SL MoSin various surface coverages grown on two STO substrates with a different initial surface lattice, the STO(001)(4 × 2) and STO(111)-(9/5 × 9/5) reconstructed surfaces, respectively. Scanning tunneling microscopy shows that epitaxial alignment of the SL MoSis present for both systems, reflected by orientation of MoSedges and a distinct moiré pattern visible on the MoS(0001) basal place. Upon increasing the SL MoScoverage, the presence of four distinct rotational domains on the STO(001) substrate, whilst only two on STO(111), is seen to control the possibilities for the formation of coherent MoSdomains with the same orientation. The presented methodology relies on standard PVD in ultra-high vacuum and it may be extended to other systems to help explore pristine two-dimensional transition metal dichalcogenide/STO systems in general.