Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope

Abstract

Carpick, Robert W.; Agraït, N.; Ogletree, D. F.; and Salmeron, Miguel, "Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope" (1996). Departmental Papers (MEAM). 97. http://repository.upenn.edu/meam_papers/97Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope AbstractWe 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. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Sec. London Ser. A 324, 301 (1971)] of elastic adhesive contacts. The friction-load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area-load relation for nonparabolic tips, The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated. 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-Kendall-Roberts ͑JKR͒ theory ͓K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Soc. London Ser. A 324, 301 ͑1971͔͒ of elastic adhesive contacts. The friction-load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area-load relation for nonparabolic tips. The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated.

Lateral stiffness: A new nanomechanical measurement for the determination of shear strengths with friction force microscopy

“…The particular model utilized, such as the Hertz 9 or Johnson-Kendall-Roberts 10 model, depends upon the strength and range of the tipsample interaction forces 11 ͑among other things͒, which is uncertain in each case. The contact area-load relation for a single asperity also depends upon the tip shape, as demonstrated experimentally by Carpick et al 6 Furthermore, if the shear strength is not independent of load ͑pressure͒, then the load dependence of shear strength and contact area become convoluted. 4 As well, the models used neglect the effect of lateral forces upon the contact area, yet this may indeed be a significant effect 12,13 to explore.…”

“…3 -triangles͒ using a standard technique described elsewhere. 3,6,22 To see how varies with load, Eqs. ͑1͒, ͑3͒, and ͑4͒ are combined to give…”

“…We confirmed this tip to be parabolic using the sharp edges of a faceted SrTiO 3 ͑305͒ sample as described previously. 6,29 A certain value for k lever was assumed above. Methods to determine k lever if calibration uncertainties exist will be discussed elsewhere, along with detailed comments on error analysis and further measurements at other humidities and in ultrahigh vacuum ͑UHV͒.…”

“…2 Recent observations indicate that at low loads, the FFM tip can form a single asperity contact with a surface [3][4][5][6] and wearless interfacial sliding occurs. Friction appears to scale with load in proportion to the area of contact as predicted for a continuous, elastic, single asperity contact.…”

Elastic and inelastic deformations of ethylene-passivated tenfold decagonalAl−Ni−Coquasicrystal surfaces

“…[1][2][3][4] One can thus detect the onset of surface damage-inelastic deformation-with atomic-scale precision. [5][6][7][8] Previous experiments with well characterized surfaces carried out in ultrahigh vacuum ͑UHV͒ have shown that the relation between friction force and contact area can be described by the Derjaguin-Müller-Toporov 3,9 ͑DMT͒ or the Johnson-Kendall-Roberts ͑JKR͒ model, 10,11 depending on the adhesion energy and on the hardness of the contacting materials. These two models have been developed as approximations for the elastic behavior in two opposite extremes, one for soft and adhesive materials, and the other for hard and poorly adhesive ones.…”