Jiang De-en, Du Mao-Hua, Dai Sheng
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J Chem Phys. 2009 Feb 21;130(7):074705. doi: 10.1063/1.3077295.
Annealing the Ru metal that typically contains residual carbon impurities offers a facile way to grow graphene on Ru(0001) at the macroscopic scale. Two superstructures of the graphene/Ru(0001) interface with periodicities of 3.0 and 2.7 nm, respectively, were previously observed by scanning tunneling microscopy. Using first principles density functional theory, we optimized the observed superstructures and found interfacial C-Ru bonding of C atoms atop Ru atoms for both superstructures, which causes the graphene sheet to buckle and form periodic humps of approximately 1.7 A in height within the graphene sheet. The flat region of the graphene sheet, which is 2.2-2.3 A above the top Ru layer and has more C atoms occupying the atop sites, interacts more strongly with the substrate than does the hump region. We found that interfacial adhesion is much stronger for the 3.0 nm superstructure than for the 2.7 nm superstructure, suggesting that the former is the thermodynamically more stable phase. We explained the 3.0 nm superstructure's stability in terms of the interplay between C-Ru bonding and lattice matching.
对通常含有残余碳杂质的钌金属进行退火处理，为在宏观尺度上在Ru(0001)上生长石墨烯提供了一种简便的方法。先前通过扫描隧道显微镜观察到石墨烯/Ru(0001)界面的两种超结构，其周期分别为3.0和2.7纳米。使用第一性原理密度泛函理论，我们优化了观察到的超结构，发现两种超结构中Ru原子上方的C原子均存在界面C-Ru键合，这导致石墨烯片发生弯曲，并在石墨烯片内形成高度约为1.7埃的周期性凸起。石墨烯片的平坦区域位于顶部Ru层上方2.2 - 2.3埃处，且有更多的C原子占据顶部位置，与衬底的相互作用比凸起区域更强。我们发现，3.0纳米超结构的界面附着力比2.7纳米超结构强得多，这表明前者是热力学上更稳定的相。我们从C-Ru键合和晶格匹配之间的相互作用角度解释了3.0纳米超结构的稳定性。
