Selective Transfer of Rotationally Commensurate MoS₂ from an Epitaxially Grown van der Waals Heterostructure

Large-scale synthesis of high-quality two-dimensional (2D) semiconductors is critical for their incorporation in emerging electronic and optoelectronic technologies. In particular, chemical vapor deposition (CVD) of transition-metal dichalcogenides (TMDs) via van der Waals epitaxy on epitaxial graphene (EG) leads to rotationally commensurate TMDs in contrast to randomly aligned TMDs grown on amorphous oxide substrates. However, the interlayer coupling between TMDs and EG hinders the investigation and utilization of the intrinsic electronic properties of the resulting TMDs, thus requiring their isolation from the EG growth substrate. To address this issue, we report here a technique for selectively transferring monolayer molybdenum disulfide (MoS₂) from CVD-grown MoS₂-EG van der Waals heterojunctions using copper (Cu) adhesion layers. The choice of Cu as the adhesion layer is motivated by density functional theory calculations that predict the preferential binding of monolayer MoS₂ to Cu in contrast to graphene. Atomic force microscopy and optical spectroscopy confirm the large-scale transfer of rotationally commensurate MoS₂ onto SiO₂/Si substrates without cracks, wrinkles, or residues. Furthermore, the transferred MoS₂ shows high performance in field-effect transistors with mobilities of up to 30 cm²/V s and on/off ratios of up to 10⁶ at room temperature. This transfer technique can likely be generalized to other TMDs and related 2D materials grown on EG, thus offering a broad range of benefits in nanoelectronic, optoelectronic, and photonic applications.