Based on low temperature plasma chemical process

a novel non-contacting precision machining method

the Atmospheric Pressure Plasma Polishing (APPP) method

is developed. The APPP method utilizes the chemical reaction between the reactive plasma and the surface atoms to perform the atom scale removal process to avoid surface/subsurface defects. A self-fabricated system is built to implement this technology in the machining of ultra-smooth surfaces. As the key component

a capacitance coupling atmospheric pressure radio-frequency plasma torch is firstly introduced. By an atomic emission spectroscopic analysis

the atom component and relative densities of the plasma zone can be obtained. The subsequent theoretical analysis reveals that specific radical atom corresponds to certain electron transition state

which can indicate the different roles of various radical atoms in the reaction process. In initial operations

silicon wafers are machined as samples. Before applying operations

both the temperature distribution on the workpiece surface and the spatial flow field distribution in the machining process are studied qualitatively by finite element analysis. Then the subsequent temperature measuring experiments demonstrate the formation of the temperature gradient on the wafer surface predicted by the theoretical analysis and indicate a peak temperature about 90 ℃ in the center. Using a commercialized form talysurf

the machined surface is detected and the results show regular removal profiles coincide well with the flow field model. Moreover

the removal profile also indicates a 32 mm

3

/min removal rate. Using the atomic force microscopy (AFM)

the surface roughness of 0.6 nm for the machined surface is also obtained. Then the element composition and proportion are detected and analyzed by an X-ray photoelectron spectroscopy (XPS). The results also demonstrate the occurrence of the anticipated main reactions. All the experiments have proved that this APPP method has a potential for fabrications of high quality optical components.