Study on the crack formation mechanism in nano-cutting of gallium arsenide

Gallium arsenide is a typical brittle material, and crack formation is one of the most serious issues in the nanometric processing. This paper majors in studying crack formation mechanism in nano-cutting of gallium arsenide. In the molecular dynamics simulation of nano-cutting process, the main damage changes from dislocation to phase transformation with the increasing cutting speed. The amount of cracks increases with the higher cutting depth, and the deformation mode turns from ductile to a combination of ductile and brittle. Cracks appear at the boundary between amorphous layer and single crystal in the subsurface and tensile stress concentration is observed around the crack tip. The crack area is polycrystalline in the models with large tool radius. Brittle-ductile transition is observed by taper-cutting experiment of gallium arsenide, and the cutting depth is measured as 25 nm where the initial surface crack forms, which proves the low brittle-ductile transition depth of gallium arsenide. Micro cracks and polycrystals are found in the subsurface of transition area by cross section TEM, which is consistent with simulation results.