Atom-by-Atom and Sheet-by-Sheet Chemical Mechanical Polishing of Diamond Assisted by OH Radicals: A Tight-Binding Quantum Chemical Molecular Dynamics Simulation Study

Abstract

Ultraflat and damage-free single-crystal diamond is a promising material for use in electronic devices such as field-effect transistors. Diamond surfaces are conventionally prepared by the chemical mechanical polishing (CMP) method, although the CMP efficiency remains a critical issue owing to the extremely high hardness of diamond. Recently, OH radicals have been demonstrated to be potentially useful for improving the CMP efficiency for diamond; however, the underlying mechanisms are still elusive. In this work, we applied our previously developed CMP-specialized tight-binding quantum chemical molecular dynamics simulator to comprehensively elucidate the CMP mechanisms of diamond assisted by OH radicals. Our simulation results indicate that the diamond surface is oxidized by reactions with OH radicals and then a concomitant surface reconstruction takes place due to the distorted and unstable nature of the oxidized diamond surface structure. Furthermore, we interestingly reveal that the reconstruction of the diamond surface ultimately leads to two distinct removal mechanisms: (i) gradual atom-by-atom removal through the desorption of gaseous molecules (e.g., CO 2 and H 2 CO 3 ) and (ii) drastic sheet-by-sheet removal through the exfoliation of graphitic ring structures. Hence, we propose that promoting the oxidation-induced graphitization of the diamond surface may provide a route to further improving the CMP efficiency.

Atomistic Wear Mechanisms in Diamond: Effects of Surface Orientation, Stress, and Interaction with Adsorbed Molecules

“…In this case, the C–C bond breaking can be initiated through strong Si–C and O–C bonds where Si and O play as mechanically supported pilot atoms. , This event was not observed when sliding against silicon, highlighting the role of counter surfaces on the diamond polishing process. By a tight-binding quantum chemical molecular dynamics simulation, Kubo et al proposed two mechanisms of wear, i.e., atom-by-atom and sheet-by-sheet removal of diamond polishing in the presence of OH radicals acting as an oxidizing agent . In H 2 O 2 solution, it has been reported that carbon atoms can react with decomposed −H, −OH, and −O, leading to the formation of C–H, C–OH, and C–O.…”

“…Great effort has been devoted to understanding the atomic mechanisms of chemical and mechanical polishing processes of diamond surfaces, − and several mechanisms have been proposed. In particular, the sp 3 -to-sp 2 transformation has been proposed to explain the experimental observation of amorphous carbon and amorphous wear particles .…”

Nanotribological Properties of Oxidized Diamond/Silica Interfaces: Insights into the Atomistic Mechanisms of Wear and Friction by Ab Initio Molecular Dynamics Simulations

“…In addition to friction, the surface rubbing at high applied loads can initiate wear. Studies on diamond-like carbon films indicated that wear can be formed through the transformation from diamond-like to graphite-like carbon, which later was verified by molecular dynamics (MD) simulations by a pilot atom concept. , Furthermore, wear can be initiated under different forms of carbon including carbon chains, atom-by-atom, and carbon sheets . Under oxygenation, carbon removal can proceed through the desorption of CO or CO 2 , ,, suggesting the essential role of oxygen in the formation of wear.…”

Study on the atomic removal behavior and damage formation mechanism of nano cutting copper–nickel alloy with diamond tool

“…MD simulation has been widely used in the field of surface engineering of single crystal nickel, copper, tungsten, aluminum, silicon, silicon carbide, aluminum nitride, gallium nitride, diamond and other materials due to its ability to simulate the nano-machining process of material systems from the perspective of atomic motion [13][14][15][16][17][18][19][20][21]. In addition, in recent years, researchers have focused on using of MD simulation to study the microscopic removal characteristics and wear mechanism of alloy materials [22,23].…”