Atomic-scale removal mechanism of chemically enhanced diamond turning of single crystal silicon carbide

Single crystal silicon carbide (SiC) is an important wide-bandgap semiconductor material for optoelectronic applications, but its low fracture toughness combined with high resistance to plastic deformation has rendered great challenges for atomic-level diamond turning. A novel chemically enhanced diamond turning approach for Si-faced SiC single crystals was thus developed using a thermochemically active lubricant that was formulated by innovatively dissolving an eco-friendly azo compound (C 12 H 16 N 4 O 4 , ACVA) in pure polyethylene glycol (PEG). The mechanism of surface termination between Si-faced SiC and ACVA molecules and its effect on material removal were analyzed using reactive molecular dynamics (MD) simulations. The thermomechanical decomposition of PEG-based ACVA lubricants on Si-faced SiC was terminated with randomly distributed surface Si-related species composed of Si–C, Si–O and Si–H bonds. The surface terminations made Si–C bonds in SiC less resistant to breakage, which facilitated easier plastic flow for mechanical removal. Furthermore, specifically designed single grit scratching experiments were performed to empirically demonstrate that thermochemical surface termination was intensified with elevated ACVA contents and scratching temperatures, producing an amorphous SiOC layer consisting of Si–C and Si–O bonds on SiC, which thus simultaneously improved removal efficiency and surface quality.