Tip-Mediated Bandgap Tuning for Monolayer Transition Metal Dichalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Monolayer transition metal dichalcogenides (TMDs) are promising beyond graphene for advanced electronics.
• Their electronic properties are sensitive to external stimuli, offering tunable characteristics.
• Understanding and controlling these properties is crucial for device applications.

Purpose of the Study:

• To demonstrate a bandgap engineering technique in monolayer MoS₂ and PtTe₂.
• To investigate the effect of tunneling current on the electronic properties of these 2D materials.
• To explore the potential for creating novel electronic functionalities, such as semiconductor-to-metal transitions.

Main Methods:

• Utilized scanning tunneling microscopy/spectroscopy (STM/STS) to probe and manipulate monolayer TMDs.
• Applied varying tunneling currents as a control parameter to induce changes in electronic structure.
• Performed theoretical calculations to understand the observed phenomena.

Main Results:

• Monolayer MoS₂ exhibited a logarithmic decrease in bandgap with increasing tunneling current, attributed to electric-field-induced gap renormalization.
• Monolayer PtTe₂ showed a significantly stronger bandgap reduction.
• A reversible semiconductor-to-metal transition was observed in monolayer PtTe₂ at moderate tunneling currents, a behavior not seen in its bulk form.

Conclusions:

• Bandgap engineering is achievable in TMD monolayers using electrical currents.
• Monolayer PtTe₂ displays unique switching behavior due to its surface electronic structure's coupling with the tunneling tip.
• These findings highlight the potential of TMD monolayers for next-generation electronic devices with tunable properties.