Learn More
We have studied the variation of frictional force with externally applied load for a Pt-coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum. At low loads, the frictional force varies with load in almost exact proportion to the area of contact as predicted by the Johnson-KendallRoberts ( JKR) theory [K. L.(More)
We have characterized mechanical properties of ultrananocrystalline diamond UNCD thin films grown using the hot filament chemical vapor deposition HFCVD technique at 680 °C, significantly lower than the conventional growth temperature of 800 °C. The films have 4.3% sp2 content in the near-surface region as revealed by near edge x-ray absorption fine(More)
Individual multiwalled carbon nanotubes with a range of aspect ratios are subjected to cyclic axial compression to large strains using atomic force microscopy. Distinct elastic buckling and post-buckling phenomena are observed reproducibly and are ascribed to Euler, asymmetric shell buckling (i.e., kinking), and symmetric shell buckling. These show(More)
Using the quasistatic Tomlinson model as a simple representation of an atomic force microscope, conditions for transitions in atomic-scale friction behavior from smooth sliding to single slips and then multiple slip regimes are derived based on energy minimization. The calculations predict and give a general explanation for transitions between different(More)
Recent molecular level studies of energy dissipation in sliding friction have suggested a contribution from adhesive forces. In order to observe this directly, we have constructed a scanning force microscope with decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and attractive forces. Measurements made on(More)
Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon oxide) to those of their bulk counterparts. Measurements down to single atomic sheets revealed that(More)
Wear of sliding contacts leads to energy dissipation and device failure, resulting in massive economic and environmental costs. Typically, wear phenomena are described empirically, because physical and chemical interactions at sliding interfaces are not fully understood at any length scale. Fundamental insights from individual nanoscale contacts are crucial(More)
We use atomic force microscopy (AFM) to determine the frictional properties of nanoscale single-asperity contacts involving octadecyltrichlorosilane (OTS) monolayers and silicon. Quantitative AFM measurements in the wearless regime are performed using both uncoated and OTS-coated silicon AFM tips in contact with both uncoated and OTS-coated silicon(More)
Understanding friction and wear at the nanoscale is important for many applications that involve nanoscale components sliding on a surface, such as nanolithography, nanometrology and nanomanufacturing. Defects, cracks and other phenomena that influence material strength and wear at macroscopic scales are less important at the nanoscale, which is why(More)
Earthquakes have long been recognized as being the result of stick-slip frictional instabilities. Over the past few decades, laboratory studies of rock friction have elucidated many aspects of tectonic fault zone processes and earthquake phenomena. Typically, the static friction of rocks grows logarithmically with time when they are held in stationary(More)