Size-tunable synthesis of monolayer MoS₂ nanoparticles and their applications in non-volatile memory devices

We report the CVD synthesis of a monolayer of MoS₂ nanoparticles such that the nanoparticle size was controlled over the range 5-100 nm and the chemical potential of sulfur was modified, both by controlling the hydrogen flow rate during the CVD process. As the hydrogen flow rate was increased, the reaction process of sulfur changed from a "sulfiding" process to a "sulfo-reductive" process, resulting in the growth of smaller MoS₂ nanoparticles on the substrates. The size control, crystalline quality, chemical configuration, and distribution uniformity of the CVD-grown monolayer MoS₂ nanoparticles were confirmed. The growth of the MoS₂ nanoparticles at different edge states was studied using density functional theory calculations to clarify the size-tunable mechanism. A non-volatile memory device fabricated using the CVD-grown size-controlled 5 nm monolayer MoS₂ nanoparticles as a floating gate showed a good memory window of 5-8 V and an excellent retention period of a decade.