Epitaxial growth of monolayer MoSe2 on GaAs.

We realized 1–4 monolayer MoSe₂ films on Se-terminated GaAs (111)B 2-in. substrates by molecular beam epitaxy. Atomically flat GaAs wafers were prepared by the migration-enhanced epitaxy method, and MoSe₂ layers were successfully grown on Se-terminated GaAs (111)B surfaces with layer-number control over the entire wafer area. The obtained MoSe₂ crystal is well aligned on the GaAs (111)B surface. The quasi-van der Waals gap formed between a Se-terminated GaAs (111)B surface and MoSe₂ was directly observed with a scanning transmission electron microscope. All A_1g Raman peaks from 93 points on 2-in. monolayer MoSe₂ are distributed within 0.25 cm⁻¹, indicating excellent spatial uniformity. [ABSTRACT FROM AUTHOR]