Layer-controlled CVD growth of large-area two-dimensional MoS₂ films

In spite of the recent heightened interest in molybdenum disulfide (MoS₂) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS₂ films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS₂ films can be achieved by treating the surfaces of their bottom SiO₂ substrates with the oxygen plasma process. Raman mapping, UV-Vis, and PL mapping are performed to show that mono, bi, and trilayer MoS₂ films grown on the plasma treated substrates fully cover the centimeter scale substrates with a uniform thickness. Our TEM images also present the single crystalline nature of the monolayer MoS₂ film and the formation of the layer-controlled bi- and tri-layer MoS₂ films. Back-gated transistors fabricated on these MoS₂ films are found to exhibit the high current on/off ratio of ∼10⁶ and high mobility values of 3.6 cm² V^-1 s^-1 (monolayer), 8.2 cm² V^-1 s^-1 (bilayer), and 15.6 cm² V^-1 s^-1 (trilayer). Our results are expected to have a significant impact on further studies of the MoS₂ growth mechanism as well as on the scaled layer-controlled production of high quality MoS₂ films for a wide range of applications.