Atomistic wear mechanisms and deformation evolution in polishing

Abstract

Our aim with this study was a new insight into the sub-nanoscale of polishing and provides the atomic view of the material removal and wear mechanisms by carrying out molecule dynamics simulation. We proposed and analyzed a model with a diamond abrasive particle that sliding or rolling on the surface of GaN workpieces. The authors investigated, step by step, the effects of polishing depths, speeds, abrasive sizes, and crystalline orientations on the wear mechanisms and material removal. The wear mechanisms of the sliding motion were adhering, ploughing, and cutting, depending on the depths. While the wear mechanisms of rolling motion are adhering and ploughing. Notably, in both stages of sliding and rolling, there is an existence of a critical point at 5.0 Å depth when we considered the deformation behaviors. Below that critical point, the GaN workpiece will present an elastic deformation. From the aforementioned point, the workpiece would be plastically deformed. Besides, from 10 Å depth, the dislocation began to appear and evolute simultaneously with the development of the maximum shear stress. The sliding motion on the Ga-face could remove a greater number of atoms than that of the N-face. Moreover, direction [1-100] on Ga-face requesting more forces to polish than direction [11-20]. In conclusion, the main achievements that contribute to the field can be summarized as follows: the atomistic wear mechanisms of sliding and rolling motions, material removal, and the role of rolling motion at the sub-nanoscale during the ultrafine flat polishing process.