Room-temperature solution processing of high-mobility MoS2 thin films

Chemical vapor deposition (CVD) has been the prevailing approach to synthesize high-quality 2D molybdenum disulfide (MoS2) for electronic devices. However, it typically requires a high synthetic temperature (e.g., 400-900 ˚C) and is thus costly and incompatible with flexible plastic substrates. Here we report the low-thermal-budget (e.g., at room temperature) solution-based deposition of high-mobility wafer-scale semiconducting MoS2 thin films, enabled by a polymer-free alkylammonium-capped MoS2 ink. In contrast to conventional long-chain polymer surfactants, the compact alkylammonium ligands exhibit adequate binding to MoS2 and can be washed away by solvent to restore atomically clean and organics-free MoS2 thin films. Therefore, the polymer-free ink provides a potential solution to the long-standing trade-off between thermal budget and electrical performance in MoS2. We show room-temperature-processed MoS2 thin films exhibiting an average electron mobility of 50 cm2·V-1·s-1, which can be further improved to 68 cm2·V-1·s-1 with 200 °C processing. The resulting transistors show a high degree of uniformity and can be readily implemented for scalable logic integration, ring oscillators, and driving circuits for organic light-emitting diodes. Especially, the fabricated MoS2 ring oscillator outputs an oscillation frequency of > 300 kHz, showing promising applications in functional circuits based on layered semiconductors. The technological applicability of 2D semiconductor thin films is normally limited by the trade-off between their synthesis temperature and electrical performance. Here, the authors report a low-temperature polymer-free solution-based method to deposit high-mobility wafer-scale MoS2 thin films, showing large-scale logic circuits and heterogeneous device integration.