Atomically Smooth Stress-Corrosion Cleavage of a Hydrogen-Implanted Crystal

Abstract

We present a quantum-accurate multiscale study of how hydrogen-filled discoidal "platelet" defects grow inside a silicon crystal. Dynamical simulations of a 10-nm-diameter platelet reveal that H2 molecules form at its internal surfaces, diffuse, and dissociate at its perimeter, where they both induce and stabilize the breaking up of highly stressed silicon bonds. A buildup of H2 internal pressure is neither needed for nor allowed by this stress-corrosion growth mechanism, at odds with previous models. Slow platelet growth up to micrometric sizes is predicted as a consequence, making atomically smooth crystal cleavage possible in implantation experiments.

Seamless elastic boundaries for atomistic calculations

“…This situation arises in studies of contact and friction in scanning probe experiments 1,2 or between atomically rough surfaces 3,4 , and fracture of brittle 5 or ductile 6 materials. The elastic response of the supporting solid can also appreciably influence chemi-and physisorption processes at crystal surfaces, including stress corrosion 7 and thin film growth 8 .…”

“…There has been great recent interest in accelerating such simulations by treating each spatial region with the modeling method that most efficiently captures material response [5][6][7][9][10][11][12] .…”

In situ growth and coalescence of He-filled bi-dimensional defects in Si by H supply

“…These observations agree with dynamical simulations as well as experiments conducted on the disk-shaped defects involving H, for which their growth is controlled by a subcritical stress-corrosion mechanism. 6,24 Moreover, during its planar growth, the He-plate stays over-pressurized due to the formation of H 2 inside the plate. Thus there are two roles of H, a chemical action in breaking Si-Si bonds together with a physical action of internal gas pressure.…”

“…9,10 The processes of exfoliation/blistering are however similar: the high internal pressure of He-plates associated with the embrittlement effect of H cause the coalescence of these nano-sized defects and then the propagation of microcracks in the material. 6,11,12 Very little works have been reported on the crack propagation during thermal annealing, even on the most-studied area of H-platelets in the Smart-Cut process. This is mainly due to the multi-scale nature of the phenomenon.…”

“…[3][4][5] Hydrogen atoms induce bond-breaking and internal surface passivation. 2,6,7 Helium, on the other hand, does not chemically interact with silicon. Its action is only physical providing a higher internal pressure than H 2 molecules thus enhancing the development and propagation of cracks.…”