Controllable synthesis of high-aspect-ratio monolayer MoS₂ nano-microribbons for high-performance phototransistors

Low-dimensional molybdenum disulfide (MoS2) is a versatile platform for ultrathin electronic, optoelectronic, and quantum devices, owing to the unique properties emerged in the reduced dimensionality. However, it remains challenging to develop facile synthesis methods for explicit control of their morphology and dimensionality. Herein, a simple and cost-effective method is developed for fast and controllable synthesis of monolayer MoS2 nano-microribbons. A mixed aqueous solution of Na2MoO4 and NaOH was spin-coated on a sapphire substrate and sulfurated via a one-step chemical vapor deposition. NaOH concentration can control the morphology and orientation distribution of MoS2, while the growth time can control the thickness of MoS2. Notably, highquality monolayer MoS2 nano-microribbons with aspect ratios over 100 and widths as narrow as 200 nm were successfully synthesized, as confirmed by optical microscopy, scanning electron microscopy, atomic force microscopy, and Raman and photoluminescence spectroscopies. In addition, a phototransistor was fabricated based on the monolayer MoS2 nanomicroribbons, demonstrating an excellent current on/off ratio of 9 x 10(5), a high photo-to-dark current ratio of 10(5), and a strong responsivity of 8.6 A W-1. Therefore, this work presents an alternative pathway for the synthesis of high-aspectratio MoS2 ribbons, which could inspire their applications for ultrathin electronic and optoelectronic devices.