LAUSR

In this article, an effective way of chemical modification on the dielectric surface (Al₂O₃) is investigated to chemical vapor deposition (CVD)-grown high-quality monolayer MoS₂ and the relevant back-gated FETs are fabricated without MoS₂ transfer. As a result, the size of the triangle MoS₂ is increased and its quality is improved as the surface of Al₂O₃ is treated by H₂SO₄. Furthermore, as compared with the gate dielectrics of the SiO₂ and as-deposited Al₂O₃, the fabricated transistor with the H₂SO₄-treated Al₂O₃ as gate dielectric achieves better electrical properties: high carrier mobility of 12.9 cm²/Vs (~10 times higher than the untreated sample, ~5.2 times higher than the SiO₂ gate-dielectric sample), small subthreshold swing of 110 mV/dec, and high ON/OFF ratio of $3\times 10^{{6}}$ . The involved mechanisms are attributed to the fact that the H₂SO₄-treated Al₂O₃ not only can increase its surface roughness to promote the nucleation and high-quality growth of MoS₂ but also can improve the quality of the MoS₂/Al₂O₃ interface. This simple chemical-modification treatment will open up an effective approach of combining the high-crystallinity CVD-MoS₂ with the high- ${k}$ dielectric without MoS₂ transfer required.