High-Quality CVD-MoS2 Synthesized on Surface-Modified Al2O3 for High-Performance MoS2 Field-Effect Transistors

In this article, an effective way of chemical modification on the dielectric surface (Al ₂ O ₃ ) is investigated to chemical vapor deposition (CVD)-grown high-quality monolayer MoS ₂ and the relevant back-gated FETs are fabricated without MoS ₂ transfer. As a result, the size of the triangle MoS ₂ is increased and its quality is improved as the surface of Al ₂ O ₃ is treated by H ₂ SO ₄ . Furthermore, as compared with the gate dielectrics of the SiO ₂ and as-deposited Al ₂ O ₃ , the fabricated transistor with the H ₂ SO ₄ -treated Al ₂ O ₃ as gate dielectric achieves better electrical properties: high carrier mobility of 12.9 cm ² /Vs (~10 times higher than the untreated sample, ~5.2 times higher than the SiO ₂ gate-dielectric sample), small subthreshold swing of 110 mV/dec, and high ON/OFF ratio of 3 × 10 ⁶ . The involved mechanisms are attributed to the fact that the H ₂ SO ₄ -treated Al ₂ O ₃ not only can increase its surface roughness to promote the nucleation and high-quality growth of MoS ₂ but also can improve the quality of the MoS ₂ /Al ₂ O ₃ interface. This simple chemical-modification treatment will open up an effective approach of combining the high-crystallinity CVD-MoS ₂ with the high-k dielectric without MoS ₂ transfer required.