Surface-Force-Induced Nonelastic Deformations Between Micrometer Size Glass Particles and Silicon Substrates

Glass beads having radii between 3 μm to 25 μm were gently deposited onto a polished silicon wafer, and the surface-force-induced particle-substrate contact radii were determined using scanning electron microscopy. The contact radii were found to vary as the particle radii to the 0.42 power (± 0.14), which is consistent with the plastic deformation model of Maugis and Pollock, 10 but inconsistent with the predictions of the elastic-response based adhesion models proposed by Johnson, Kendall, and Roberts 5 or Derjaguin, Muller, and Toporov. 6 Estimates of the stresses due to the surface forces suggest that they exceed the tensile strength of glass and that the observed deformations can arise from these tensile stresses.