Growth of singly orientated MoSe2 monolayer on Al2O3(11(2)over-bar0)

Singly oriented MoSe2 monolayer has been epitaxially grown on the Al2O3(11 (2) over bar0) substrate using molecular beam epitaxy (MBE). Based on the evolution of the optical anisotropy of growing MoSe2 layer monitored in-situ and in real-time, the growth can be divided into two steps: small island growth and subsequent coalescence. Manipulated by the two-fold lattice symmetry of the substrate surface, MoSe2 nuclei and domains orientate themselves preferentially by aligning their zig-zag direction along the Al2O3[0001] direction. This preferential orientation maintains during coalescence leading to the formation of singly oriented monolayer. The increase of the optical anisotropy of MoSe2 throughout the island growth indicates the dominating interfacial interplay with substrate surface, whereas its decrease actuated by coalescence signifies the overtaking of the lateral interaction within MoSe2 monolayer. Our results reveal the detailed growth mechanism of the van der Waals epitaxial of single crystal 2D layer guided by the surfaces with reduced lattice symmetry.

Automated summary

A singly oriented MoSe2 monolayer was grown on an Al2O3(11 (2) over bar0) substrate using molecular beam epitaxy (MBE). The growth process can be divided into small island growth and subsequent coalescence, with MoSe2 nuclei and domains preferentially aligning their zig-zag direction along the Al2O3[0001] direction due to the two-fold lattice symmetry of the substrate surface. The increase and decrease of optical anisotropy during island growth and coalescence, respectively, indicate the dominance of interfacial interaction with the substrate surface and the lateral interaction within the MoSe2 monolayer.