An emerging electronic material as one of transition metal dichalcogenides (TMDCs), tungsten disulfide (WS₂) can be exfoliated as an atomically thin layer and can compensate for the drawback of graphene originating from a gapless band structure. A direct bandgap, which is obtainable in single-layer WS₂, is an attractive characteristic for developing optoelectronic devices, as well as field-effect transistors. However, its relatively low mobility and electrical characteristics susceptible to environments remain obstacles for the use of device materials. Here, we demonstrate remarkable improvement in the electrical characteristics of single-layer WS₂field-effect transistor (SL-WS₂FET) using chemical vapor deposition (CVD)-grown hexagonal BN (h-BN). SL-WS₂FET sandwiched between CVD-grown h-BN films shows unprecedented high mobility of 214 cm²/Vs at room temperature. The mobility of a SL-WS₂FET has been found to be 486 cm²/Vs at 5 K. The ON/OFF ratio of output current is ~10⁷at room temperature. Apart from an ideal substrate for WS₂FET, CVD-grown h-BN film also provides a protection layer against unwanted influence by gas environments. The h-BN/SL-WS₂/h-BN sandwich structure offers a way to develop high-quality durable single-layer TMDCs electronic devices.

We report a simple and mass-scalable approach for thin MoS₂ films via RF sputtering combined with the post-deposition annealing process. We have prepared as-sputtered film using a MoS₂ target in the sputtering system. The as-sputtered film was subjected to post-deposition annealing to improve crystalline quality at 700 °C in a sulfur and argon environment. The analysis confirmed the growth of continuous bilayer to few-layer MoS₂ film. The mobility value of ~29 cm²/Vs and current on/off ratio on the order of ~10⁴ were obtained for bilayer MoS₂. The mobility increased up to ~173–181 cm²/Vs, respectively, for few-layer MoS₂. The mobility of our bilayer MoS₂ FETs is larger than any previously reported values of single to bilayer MoS₂ grown on SiO₂/Si substrate with a SiO₂ gate oxide. Moreover, our few-layer MoS₂ FETs exhibited the highest mobility value ever reported for any MoS₂ FETs with a SiO₂ gate oxide. It is presumed that the high mobility behavior of our film could be attributed to low charged impurities of our film and dielectric screening effect by an interfacial MoO_xSi_y layer. The combined preparation route of RF sputtering and post-deposition annealing process opens up the novel possibility of mass and batch production of MoS₂ film.

In this article, we report layer-controlled, continuous and large-area molydenum sulfide (MoS₂) growth onto a SiO₂/Si substrate by RF sputtering combined with sulfurization. A two-step process was employed to synthesize MoS₂ films. In the first step, an atomically thin MoO₃ film was deposited by RF magnetron sputtering at 300 °C. Subsequently, the as-sputtered MoO₃ film was further subjected to post-annealing and sulfurization processes at 650 °C for 1 hour. It was observed that the number of layers of MoS₂ can be controlled by adjusting the sputtering time. The fabricated MoS₂ transistors exhibited high mobility values of ∼21 cm² V⁻¹ s⁻¹ (bilayer) and ∼25 cm² V⁻¹ s⁻¹ (trilayer), on/off ratios in the range of ∼10⁷ (bilayer) and 10⁴–10⁵ (trilayer), respectively. We believe that our proposed paradigm can start a new method for the growth of MoS₂ in future electronics and optoelectronics applications.