Unusual Thickness-Dependent Friction on CuInP_{2}S_{6} Originating from Work-Function Regulation

Area of Science:

• Materials Science
• Tribology
• Condensed Matter Physics

Background:

• Friction in two-dimensional (2D) materials typically decreases with increasing thickness.
• Understanding thickness-dependent friction is crucial for designing advanced nanoelectronic and MEMS devices.

Purpose of the Study:

• To investigate the unconventional thickness dependence of friction in 2D copper indium phosphorus sulfide (CuInP2S6) nanosheets.
• To elucidate the underlying physical mechanism responsible for this anomalous friction behavior.

Main Methods:

• Experimental measurements using Kelvin Probe Force Microscopy (KPFM).
• Theoretical analysis employing first-principles calculations.
• Fabrication of 2D CuInP2S6 nanosheets on silicon substrates.

Main Results:

• Observed enhanced friction with increasing thickness of CuInP2S6 nanosheets, contrary to conventional trends.
• Identified a work-function regulated friction mechanism.
• Demonstrated that decreasing work function with increasing thickness leads to stronger interfacial interactions and higher friction.

Conclusions:

• The study reveals an anomalous thickness-dependent friction in ferroelectric 2D materials.
• Work function modulation is identified as the key factor governing friction in these systems.
• Suggests work-function engineering as a viable strategy for active friction control in 2D materials.