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Friction between van der Waals Solids during Lattice Directed Sliding
Paul E Sheehan1,2, Charles M Lieber2
1U.S. Naval Research Laboratory, Code 6177, Washington, DC 20375, United States.
Nano Letters
|June 2, 2017
Summary
Researchers studied sliding molybdenum trioxide (MoO3) nanocrystals on transition metal dichalcogenides. They found friction depends on nanocrystal size and sliding conditions, with lower friction than expected for nanoscale systems.
Area of Science:
- Materials Science
- Nanotechnology
- Surface Science
Background:
- Two-dimensional materials like molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) are crucial in nanoscale electronics.
- Understanding interfacial properties is key for developing novel nanoscale devices.
Purpose of the Study:
- To investigate the friction and interfacial shear strength of nanometer-scale molybdenum trioxide (MoO3) crystals on MoS2 and MoSe2 substrates.
- To explore the influence of nanocrystal size, sliding velocity, and substrate commensuration on friction.
Main Methods:
- Formation of MoO3 nanocrystals on MoS2 and MoSe2 substrates.
- Utilizing atomic force microscopy (AFM) to oscillate and slide nanocrystals.
- Measuring lateral forces to determine interfacial shear strength.
Main Results:
- Lateral friction force increased linearly with MoO3 nanocrystal area.
- Interfacial shear strength was significantly lower than in macroscale systems.
- Friction depended strongly on sliding duration and velocity, suggesting a thermal activation model.
- Lower substrate commensuration unexpectedly increased interfacial shear, contradicting theoretical predictions.
Conclusions:
- Nanoscale friction of MoO3 on transition metal dichalcogenides is size-dependent and influenced by sliding dynamics.
- The observed friction behavior deviates from macroscale expectations and theoretical models, highlighting unique nanoscale phenomena.
- Further research is needed to fully elucidate the mechanisms governing interfacial shear strength at the nanoscale.
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