Controllable Growth of MoS2 Nanospirals by Using Sodium Dodecyl Sulfate as a Seeding Promoter for Photodetection Devices

Due to their unique spiral structure, transition metal dichalcogenide (TMDC) nanospirals have shown unique electronic and optical properties and have been widely explored in the fields of hydrogen evolution reaction, optoelectronics, and nonlinear optics. Many TMDC nanospirals have been successfully synthesized by using the chemical vapor deposition (CVD) method. The precursor ratio and growth temperature were well regulated to grow various nanospirals. However, the influence of the concentration of the seeding promoter on growing TMDC nanospirals is unexplored. In this work, we use sodium dodecyl sulfate (SDS) as the seeding promoter to grow MoS₂ in the CVD process. MoS₂ nanosheets were controllably grown by using SDS with a high concentration, while MoS₂ nanospirals were obtained when SDS with a low concentration was used. Optical microscopy and atomic force microscopy (AFM) measurements showed that the MoS₂ nanospirals were uniformly distributed on small-sized monolayer MoS₂ nanosheets. The twist angle between the bottom MoS₂ spiral layer and monolayer nanosheet and the Moiré patterns were revealed by high-resolution transmission electron microscopy. The MoS₂ nanospiral-based device exhibits better optoelectronic performance than a nanosheet-based device, including carrier mobility, photoresponsivity, photosensitivity, and response time. Photoconductive AFM measurement shows that the photocurrent of the nanospiral is higher than that of the nanosheet. The excellent optoelectronic performance of MoS₂ nanospirals could be ascribed to the vertical conductivity, superior dielectric screening, and strain in the spiral step, which arise from the unique spiral structure. Our work indicates that the MoS₂ nanospiral could be used for the high-performance optoelectronic device.