Imaging the Quantum Capacitance of Strained MoS₂ Monolayers by Electrostatic Force Microscopy.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum disulfide (MoS2) monolayers are semiconducting transition metal dichalcogenides with tunable optoelectronic properties.
• Strain engineering is a key method to modify MoS2 properties for advanced applications.
• Understanding charge carrier behavior in strained MoS2 is crucial for next-generation electronics.

Purpose of the Study:

• To investigate the electric field response of biaxially strained MoS2 monolayers using RF-EFM.
• To differentiate the intrinsic quantum capacitance of strained MoS2 from contributions of atomic-scale defects.
• To develop a nanoscale, noninvasive imaging technique for probing quantum phenomena.

Main Methods:

• Implementation of radio frequency-assisted electrostatic force microscopy (RF-EFM) at 300 MHz.
• Production of strained MoS2 monolayers in mesoscopic bubbles via H-ion irradiation.
• Simultaneous imaging of bubble topography and quantum capacitance.

Main Results:

• RF-EFM successfully distinguished intrinsic quantum capacitance from defect-related capacitance in strained MoS2.
• At high RF frequencies (300 MHz), defect contributions to capacitance and transport become negligible.
• The technique allowed visualization of both topography and quantum capacitance at the nanoscale.

Conclusions:

• RF-EFM is a powerful tool for probing the intrinsic electronic properties of strained 2D materials.
• This method enables the study of time- and spatial-dependent phenomena like electron compressibility.
• The technique offers a noninvasive approach to investigate quantum materials.