Topography-Selective Removal of Atmospheric Pressure Plasma Polishing

Atmospheric pressure plasma polishing (APPP) is an efficient method to produce damage-free ultra-smooth surfaces, due to its chemical nature. APPP works intelligently on distinguishing surface micro-topographies, thereby realizing diverse reaction rates on different surface morphologies. Since the convex surface structures are always removed faster than the concave structures by dry etching process, the whole surface roughness can be reduced further to form ultra-smooth surfaces. Quantum chemistry simulation of two groups of models has been utilized to prove the conclusion in theory. Afterward, practical machining experiments have been conducted, in which the sample is detected every 40 s by atomic force microscopy to testify the decrease of surface roughness. Experimental results accord well with theoretical simulation. The machined sample is also detected by scanning electronic microscopy and nano-mechanical test system. The mechanical properties are demonstrated to be improved by APPP process, especially the residual stress is reduced by about 4.2 GPa after 60 s machining. The micro-topography is also indicated more regular, and finally reaches below Ra 0.5 nm surface roughness.