Bandgap tunability at single-layer molybdenum disulphide grain boundaries

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition metal dichalcogenides (TMDs) are novel semiconductor materials with unique electronic and optical properties.
• Single-layer molybdenum disulphide (MoS2) is a key prototype TMD with thickness-dependent electronic bandgap.

Purpose of the Study:

• To measure the quasiparticle energy gap of MoS2 with varying layer thicknesses.
• To investigate the influence of grain boundaries on the bandgap of single-layer MoS2.
• To explore the potential for tunable bandgaps in MoS2 for advanced electronic applications.

Main Methods:

• High-resolution scanning tunnelling microscopy (STM) and spectroscopy were employed.
• MoS2 films were synthesized on a graphite substrate using chemical vapour deposition (CVD).
• Quasiparticle energy gaps were measured for single-layer, bilayer, and trilayer MoS2.

Main Results:

• Measured quasiparticle energy gaps: 2.40 ± 0.05 eV (single-layer), 2.10 ± 0.05 eV (bilayer), and 1.75 ± 0.05 eV (trilayer) MoS2.
• Observed significant bandgap tunability (up to 0.85 ± 0.05 eV) in single-layer MoS2 near grain boundaries.
• Demonstrated that bandgap tunability depends on distance from grain boundaries and grain misorientation angle.

Conclusions:

• MoS2 exhibits thickness-dependent bandgaps, crucial for nanoelectronic applications.
• Grain boundary engineering in MoS2 offers a novel pathway for achieving tunable bandgaps.
• This research paves the way for flexible electronic and optoelectronic devices with precisely controlled bandgap properties.