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
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
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DOI：
10.1021/acsami.1c09468
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发表时间：
2021-08-17
影响因子：
9.5
通讯作者：
Kubo, Momoji
中科院分区：
文献类型：
--
作者：
Kawaguchi, Kentaro;Wang, Yang;Kubo, Momoji
超平坦且无损伤的单晶金刚石是一种很有前景的材料，可用于场效应晶体管等电子设备。金刚石表面通常通过化学机械抛光（CMP）方法制备，但由于金刚石硬度极高，CMP 效率仍然是一个关键问题。最近，OH 自由基已被证明可用于提高金刚石的 CMP 效率；然而，根本机制仍然难以捉摸。在这项工作中，我们应用之前开发的CMP专用紧束缚量子化学分子动力学模拟器来全面阐明OH自由基辅助金刚石的CMP机理。我们的模拟结果表明，金刚石表面通过与 OH 自由基的反应而被氧化，然后由于氧化金刚石表面结构的扭曲和不稳定性质而发生伴随的表面重建。此外，我们有趣地发现，金刚石表面的重建最终导致两种不同的去除机制：（i）通过气态分子（例如CO2和H2CO3）的解吸逐渐逐个原子去除和（ii）通过石墨环结构的剥落逐片剧烈去除。因此，我们建议促进金刚石表面的氧化诱导石墨化可能为进一步提高 CMP 效率提供一条途径。
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., CO2 and H2CO3) 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.