Cheng Ting, Liu Zhirong, Liu Zhongfan, Ding Feng
College of Chemistry and Molecular Engineering, Center for Nanochemistry, Academy for Advanced Interdisciplinary Studies, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, China.
Beijing Graphene Institute, Beijing 100095, China.
ACS Nano. 2021 Apr 27;15(4):7399-7408. doi: 10.1021/acsnano.1c00776. Epub 2021 Mar 22.
Wafer-scale single-crystal graphene film directly grown on insulating substrates the chemical vapor deposition (CVD) method is desired for building high-performance graphene-based devices. In comparison with the well-studied mechanism of graphene growth on transition metal substrates, the lack of understanding on the mechanism of graphene growth on insulating surfaces greatly hinders the progress. Here, by using first-principles calculation, we systematically explored the absorption of various carbon species CH ( = 0, 1, 2, 3, 4) on three typical insulating substrates [-BN, sapphire, and quartz] and reveal that graphene growth on an insulating surface is dominated by the reaction of active carbon species with the hydrogen-passivated graphene edges and thus is less sensitive to the type of the substrate. The dominating gas phase precursor, CH, plays two key roles in graphene CVD growth on an insulating substrate: (i) to feed the graphene growth and (ii) to remove excessive hydrogen atoms from the edge of graphene. The threshold reaction barriers for the growth of graphene armchair (AC) and zigzag (ZZ) edges were calculated as 3.00 and 1.94 eV, respectively; thus the ZZ edge grows faster than the AC one. Our theory successfully explained why the circumference of a graphene island grown on insulating substrates is generally dominated by AC edges, which is a long-standing puzzle of graphene growth. In addition, the very slow graphene growth rate on an insulating substrate is calculated and agrees well with existing experimental observations. The comprehensive insights on the graphene growth on insulating surfaces at the atomic scale provide guidance on the experimental design for high-quality graphene growth on insulating substrates.
直接生长在绝缘衬底上的晶圆级单晶石墨烯薄膜，化学气相沉积（CVD）方法对于构建高性能石墨烯基器件是很有必要的。与在过渡金属衬底上已被充分研究的石墨烯生长机制相比，对石墨烯在绝缘表面生长机制的缺乏了解极大地阻碍了进展。在此，通过使用第一性原理计算，我们系统地探索了各种碳物种CH（= 0、1、2、3、4）在三种典型绝缘衬底[-BN、蓝宝石和石英]上的吸附，并揭示了在绝缘表面上石墨烯的生长主要由活性碳物种与氢钝化的石墨烯边缘的反应主导，因此对衬底类型不太敏感。主要的气相前驱体CH在绝缘衬底上的石墨烯CVD生长中起两个关键作用：（i）为石墨烯生长提供原料，（ii）从石墨烯边缘去除过量的氢原子。计算出石墨烯扶手椅（AC）边缘和锯齿（ZZ）边缘生长的阈值反应势垒分别为3.00和1.94 eV；因此ZZ边缘比AC边缘生长得更快。我们的理论成功地解释了为什么在绝缘衬底上生长的石墨烯岛的周长通常由AC边缘主导，这是石墨烯生长中一个长期存在的难题。此外，计算出在绝缘衬底上石墨烯非常缓慢的生长速率，并且与现有的实验观察结果非常吻合。在原子尺度上对石墨烯在绝缘表面生长的全面见解为在绝缘衬底上高质量石墨烯生长的实验设计提供了指导。
