Rapid In-Situ Synthesis and Patterning of Edge-Unsaturated MoS by Femtosecond Laser-Induced Photo-Chemical Reaction.

Molybdenum disulfide (MoS) is a representative transition metal sulfide that is widely used in gas and biological detection, energy storage, and integrated electronic devices due to its unique optoelectrical and chemical characteristics. To advance toward the miniaturization and on-chip integration of functional devices, it is strategically important to develop a high-precision and cost-effective method for the synthesis and integration of MoS patterns and functional devices. Traditional methods require multiple steps and time-consuming processes such as material synthesis, transfer, and photolithography to fabricate MoS patterns at the desired region on the substrate, significantly increasing the difficulty of manufacturing micro/nanodevices. In this work, we propose a single-step femtosecond laser-induced photochemical method which can realize the fabrication of arbitrary two-dimensional edge-unsaturated MoS patterns with high efficiency in microscale. Based on this method, MoS can be synthesized at a rate of 150 μm/s, 2 orders of magnitude faster than existing laser-based thermal decomposition methods without sacrificing the resolution and quality. The morphology and roughness of the MoS pattern can be controlled by adjusting the laser parameters. Furthermore, the femtosecond laser direct writing (FLDW) method was used to fabricate microscale MoS-based gas detectors that can detect a variety of toxic gases with high sensitivity up to 0.5 ppm at room temperature. This FLDW method is not only applicable to the fabrication of high-precision MoS patterns and integrated functional devices, it also provides an effective route for the development of other micro/nanodevices based on a broad range of transition metal sulfides and other functional materials.