Influence of SiC surface defects on materials removal in atmospheric pressure plasma polishing

To study the influence of SiC surface defects on atmospheric pressure plasma polishing (APPP) process, quantum chemistry simulation and analysis is used to reveal the reaction features of typical defect topographies. Three groups of typical structures are modeled, including edge dislocation, screw dislocation and perfect crystal lattice. By using quantum chemistry calculation software, it is demonstrated that the existence of surface defects improves probability for chemical etching. The densities of states (DOS) and number of bonding electrons indicate that the defect structures have poor stability compared with perfect crystal lattice, which means defects are favorable for increasing the removal rate. The calculation results on activation energy also verify the conclusion further. Experimental machining and measurement have been performed to prove the theoretical analysis. Tests are made on selected single crystal SiC samples with different defect densities. Removal profiles measured by white light interferometer indicate that surface defects are helpful for raising the machining efficiency. But, measured surface topographies show that within certain range, surface defects deteriorate the surface roughness during the polishing process. Until most surface damage is removed, the surface roughness will be improved effectively which makes the interface smoother. Thus, the experimental investigation accords well with theoretical analysis. (C) 2018 Elsevier B.V. All rights reserved.