Strain-Assisted Large-Scale 1T-MoS₂ Synthesis and its Optical Synaptic Flash Memory Application

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition-metal dichalcogenides (TMDCs) exhibit promising electronic and optical properties for next-generation devices.
• Phase engineering in TMDCs, such as molybdenum disulfide (MoS₂), offers a pathway to enhance material performance.
• The metastable 1T phase of MoS₂ possesses distinct electronic characteristics compared to the stable 2H phase.

Purpose of the Study:

• To develop a novel synthesis method for wafer-scale 1T phase MoS₂.
• To stabilize the 1T phase against transitions to the 2H phase.
• To investigate the performance of 1T-phase MoS₂ in nonvolatile memory and optoelectronic devices.

Main Methods:

• Plasma-assisted metal-sulfidation process to synthesize MoS₂.
• Utilizing spontaneous internal strain in thicker MoS₂ layers to suppress phase transition.
• Fabrication and characterization of 1T-phase MoS₂ floating gate (1T-FG) flash memory devices.

Main Results:

• Successful synthesis of wafer-scale 1T-MoS₂ with stabilized phase.
• 1T-MoS₂ exhibits a narrow bandgap (0.4 eV) semi-metallic state with remarkable electrical properties.
• 1T-FG flash memory demonstrated a wider memory window, higher on/off ratio, and improved stability over 2H-FG devices.
• Demonstrated carrier trapping in 1T-FG memory under light irradiation, even in the off state.

Conclusions:

• A facile phase control strategy for synthesizing stable 1T-MoS₂ was established.
• The study provides insights into the potential of 1T-MoS₂ for advanced nonvolatile memory and optoelectronic synaptic functionalities.
• The developed method enables large-scale integration and highlights the advantages of the 1T phase for device applications.