AVS 65th International Symposium & Exhibition
    Tribology Focus Topic Tuesday Sessions
       Session TR-TuP

Paper TR-TuP1
Measurements of Microscale Friction on Molybdenum Disulfide using an Integrated Quartz Crystal Microbalance and Nanoindentation System

Tuesday, October 23, 2018, 6:30 pm, Room Hall B

Session: Tribology Focus Topic Poster Session
Presenter: Brian Borovsky, St. Olaf College
Authors: B.P. Borovsky, St. Olaf College
G.R. McAndrews, St. Olaf College
R.J. Wieser, St. Olaf College
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We report on experiments investigating the microtribological properties of molybdenum disulfide (MoS2) crystals in the high-speed regime. The sliding speeds obtained are over 1 m/s, corresponding to a practical range for mechanical devices. The contacts formed are approximately 1 µm across or smaller. Measurements are performed with a shear-mode quartz crystal microbalance (QCM) integrated into a nanoindentation system. For each test, a thin MoS2 crystal is adhered to the surface of a gold-coated QCM sensor and mechanically exfoliated. The resonant frequency and quality factor of the modified QCM undergo shifts when a spherical sapphire probe is loaded onto the top surface, allowing the detection of lateral contact forces. The shearing amplitude of the QCM is swept over its available range, with the load held fixed, to observe the transition from partial slip to full slip conditions. The contact area is inferred from the lateral stiffness at low amplitudes. We discuss the observed trends in the friction vs. load and area vs. load curves, as well as the degree to which the frictional shear strength depends on mean applied pressure. These results are compared to existing work on MoS2 for contacts ranging from nanometers to millimeters in size, with the aim of contributing to an improved multiscale understanding of tribological phenomena.