Atomic and close-to-atomic scale polishing of Lu2O3 by plasma-assisted etching

Abstract

This study presents a new method of in-process plasma-assisted etching (PaE) integrated with low-pressure polishing of lutetium oxide with high efficiency and without subsurface damage (SSD). The necessity of integrated low-pressure polishing is demonstrated through a quantum chemistry simulation. An improved Deal–Grove model for plasma treatment is established to predict the modification behavior. A modification rate of 136 nm/h can be obtained by simultaneously optimizing the plasma process. An atomically flat and SSD-free surface with a surface roughness in Sa of 0.14 nm is accomplished. The overall processing time is decreased to half the time of low-pressure slurry polishing. The new method is based on the OH* irradiation of lutetium oxide and the conversion of lutetium oxide into hydroxide, which rapidly reacts with 25% sulfuric acid droplets. The rapid planarization of the surface is then quickly realized by short low-pressure polishing. Finally, the in-process PaE quickly removes the SSD caused by low-pressure polishing. Aberration-corrected transmission electron microscopy of machined surfaces reveals the removal of the mechanically induced damage. The study shows that the new method has great potential as an environment-friendly processing technique in SSD-free finishing.