Ultrafast carrier dynamics of mono- and few-layer WS2 through NaCl assisted chemical vapor deposition growth
Abstract
NaCl has widely been used as a seeding promoter for chemical vapor deposition of large-scale 2D transition metal dichalcogenides. In this work, we report a study of the influence of NaCl on the growth and optical properties of layered CVD-grown WS2 using steady-state and time-resolved Kerr rotation measurements at room temperature. Strong photoluminescence (PL) signals from single flakes grown with a low NaCl content indicates direct band-gap emission, whereas flakes grown with higher amounts of NaCl exhibit red-shifted, weaker PL. Raman measurements from single flakes also indicate that WS2 grown with higher NaCl amounts result in multilayered structures, while lower NaCl quantities yield monolayer WS2. Ultrafast carrier decay measurements from single flakes also indicate a NaCl-dependent on the valley exchange interaction component (<10 ps) and slower decay components (>50 ps), attributed to a combination of phenomena, such as the band gap transitioning from direct to indirect and defect-related localized states. Our study provides insight into the influence of seeding promoters in layered CVD-grown WS2 in particular and 2D transition metal dichalcogenides in general.
Publication Title
Nanotechnology
Recommended Citation
Woli, Y., Pokhrel, H., Fu, Q., Krause, B., Pollard, S., & Hoang, T. (2025). Ultrafast carrier dynamics of mono- and few-layer WS2 through NaCl assisted chemical vapor deposition growth. Nanotechnology, 36 (34) https://doi.org/10.1088/1361-6528/adf8f4
