Effect of Substrate Orientation on MoSe₂/GaAs Heteroepitaxy

Monolayer MoSe 2 (0001) films are epitaxially grown on the (111)B-, (110)-, and (001)-oriented GaAs substrates by molecular-beam epitaxy. We found that the lattice mismatch is not a significant factor in determining the epitaxial relationship: epitaxial MoSe 2 (0001) film is formed in such a way that the directions of MoSe 2 and GaAs with the highest linear atomic densities are aligned with each other. The MoSe 2 (0001) films on GaAs(111)B and (110) show the common epitaxial relationship of MoSe 2 [112̅0]//GaAs[11̅0]. For the growth on GaAs(001), the highly anisotropic atomic structure of the initial GaAs(001) surface plays a key role in determining the epitaxial orientation; the MoSe 2 [112̅0] direction is aligned with the GaAs[110] direction but not with the orthogonal direction of GaAs[11̅0].