Ductility at the nanoscale: Deformation and fracture of adhesive contacts using atomic force microscopy

Abstract

Fracture of nanosize contacts formed between spherical probes and flat surfaces is studied using an atomic force microscope in an ultrahigh vacuum environment. Analysis of the observed deformation during the fracture process indicates significant material extensions for both gold and silica contacts. The separation process begins with an elastic deformation followed by plastic flow of material with atomic rearrangements close to the separation. Classical molecular dynamics studies show similarity between gold and silicon, materials that exhibit entirely different fracture behavior at macroscopic scale. This direct experimental evidence suggests that fracture at nanoscale occurs through a ductile process.

Electron-beam-assisted superplastic shaping of nanoscale amorphous silica

“…'Cold' superplastic deformation is thus made possible near RT, almost equivalent to flow near or above T g . In other words, the atomic-scale mechanism51213 responsible for the high-temperature thermally induced viscous flow is now rendered pronounced at RT with the help of the e-beam-induced defects.…”

“…Under high stresses, a glass can plastically deform through the bond breaking and bond-switching processes that mediate the rotation and migration of atomic clusters1213. With e-beam illumination, oxygen vacancies and ionization damage, including dangling bonds, are constantly induced throughout the material, owing to the interaction of the atoms with the incoming high-energy electrons.…”

Asperity contacts at the nanoscale: Comparison of Ru and Au

“…Materials that are macroscopically brittle may undergo some plasticity on the microscopic level. 44 In bulk Fig. 2(a).…”

Damage Accumulation in Silica Glass Nanofibers

“…The main physical mechanism invoked to explain the onset of ductility at the nanoscale involves the interplay between surface and bulk effects, whose relative importance clearly changes with the sample size. This appears to be a widely observed phenomenon, manifested not only in amorphous solids, [13][14][15][16] but, to some extent, also in crystals. 14,17,18 A "fluid-like" surface layer similar to those observed in glassy polymers 19,20 was reported in recent experiments on amorphous silica.…”