The first successful synthesis and characterization of single-crystalline two-dimensional (2D) semiconducting antimony tri oxide (Sb₂O₃) by direct chemical vapor deposition (CVD) growth on monolayer graphene is presented herein. The Sb₂O₃ flakes on graphene are regular triangles with smooth edges and a thickness of ∼1.45 nm. The thickness dependence of the Raman spectra and scanning Kelvin probe microscopy (SKPM) were systematically studied.