Atomic-scale damage control via thermochemical mechanical grinding induced amorphization of single crystal silicon carbide

Abstract Single crystal silicon carbide (SiC) is a key semiconductor material for fabricating next-generation energy-efficient optoelectronic devices. However, its high brittleness and hardness make it extremely difficult to cost-effectively machine into final substrates of atomically smooth surfaces and damage-free subsurfaces; thus, high-efficiency and low-damage grinding processes for atomic-level crystal shaping are needed. In this study, an eco-friendly thermal initiator (TI) widely used in 3D printing was innovatively dissolved in polyethylene glycol (PEG) to formulate a thermochemically active coolant for grinding SiC single crystals. The chemical reaction between TI molecules and Si-faced SiC and its effect on crystal deformation and removal were examined using temperature-controlled single grit scratching and reactive force field (ReaxFF) molecular dynamics (MD) simulations. The chemically enhanced grinding with a fine diamond wheel exhibited a deformation-controlled material removal mode, featuring ductile striations and surface amorphization with atomic-scale defects, including slight distortion of the atomic planes, stacking faults and dislocations, while brittle–ductile mixed surfaces were produced when coarse diamond wheels were used. Conversely, PEG-only lubricated grinding generated more severe surface and subsurface damage in both deformation- and fracture-controlled regimes, including microcracks, amorphous phase, stacking faults, lattice distortion and dislocations. The TI coolant-scratched SiC surface was uniformly covered by a reactant SiOC layer composed of Si–O and C–Si bonds, formed through radical attacks from heat-induced TI decomposition at low temperatures. The specifically designed scratchingexperiments and thermochemical–mechanical MD modeling revealed that compared with crystalline SiC, this amorphous SiOC layer exhibited higher microplasticity, which improved the ductile machinability of SiC and thus facilitated chip formation and removal with reduced compressive and shear stresses, followed by a smoother surface with a thinner defect layer and higher efficiency.