Atomistic origins of material removal rate anisotropy in mechanical polishing of diamond crystal

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• 作者：W.J. Zong ; ^{zongwenjun@hit.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; X. Cheng ; J.J. Zhang ; ^{zhjj505@gmail.com" class="auth_mail" title="E-mail the corresponding author}
• 刊名：Carbon
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：99
• 期：Complete
• 页码：186-194
• 全文大小：3928 K

文摘

In this work, molecular dynamics simulation is employed to represent the diamond polishing. Radial distribution function and coordination number analyses are further performed to reveal the underlying atomistic origins of the removal rate anisotropy. The results show that the lattice distortion is inevitable as the diamond substrate suffers from the mechanically induced effects, which produces an amorphous layer on the surface. In the amorphization, the perfect diamond cubic transforms to some non-diamond phases, including the amorphous sp⁰, sp¹, sp² and sp³ hybridized structures and well-arranged sp² structures. However, the dominant phases are sp² and amorphous sp³ phases. More interestingly, it is found that the removal rate strongly depends on the proportion of sp² hybridizations to amorphous sp³ structures. In the ‘hard’ direction, phase transformation from amorphous sp³ to sp² is difficult, and therefore a low proportion of sp² to amorphous sp³ appears, which results in a small removal rate. In the ‘soft’ direction, phase transformation from amorphous sp³ to sp² has less resistance, and a higher proportion output, which gives a greater removal rate. The variation laws as revealed above confirm that the removal rate anisotropy in diamond polishing is derived from the concentration of sp² hybridizations in the as-created amorphous layer and debris.