| Graphene and silicene, a couple of counterparts of thin atomic monolayers with honeycombed lattices, are the new rising stars in many fields such as physics, materials science and chemistry, causing the great rush of scientific researchers. Based on the linear dispersion, near massless fermions with ultrafast velocity are in their Dirac cone. Therefore, they are the ideal materials for ultrafast microelectronics and spintronics in future. Moreover, due to the excellent mechanical, optical, thermal properties and so on, graphene has many novel applications, e. g. sensor, detection, solar cell and supercapacity.Based on density functional theory (DFT) calculations and theory of crystal growth, the nucleation of graphene is investigated both on a well matched Ni(111) surface and on a large mismatched Rh(111) by systematically exploring the CN clusters (with size N ranging from1to24) either on a terrace or near a step edge of transition metal (TM) surface. It is surprising that incorporating one to three pentagons into a graphene island on a TM terrace is required to achieve the most stable structure. A ground state structure transformation is found firstly from a C chain to a sp2C network at N-10-12, which is corresponding to the nucleation size at a wide range of carbon chemical potential. Besides, we found that steps of both Ni(111) and Rh(111) can help’to stabilizing the hexagon and reducing the formation energy. Thus, at a relative low carbon chemical potential, the nucleation preferentially occurred along the step. In addition, two competing style of passivation for C chain, as well as the nonlinear growth behaviours were revealed along the large mismatched step of Rh(111) surface. During the research of graphene growth behaviors, a magic carbon cluster C21is intriguingly found at four selected TM surfaces, that is, Ni(111), Cu(111), Rh(111) and Ru(0001), which explained the recent observed uniformed C clusters on TM surfaces. Besides, we investigated the impact of passivation on the graphene edges on three TM surfaces [Cu(111), Co(111), and Ni(111)]. Different from that in vacuum, the pristine zz edge is stable on all TM surface and an undiscovered novel reconstructed ac(ad) edge is high stable on Co(111) and Ni(111) surfaces. Beyond this, the unique edge configuration has a significant impact on the graphene CVD growth behavior.As an extension of graphene growth work, we investigated the structures and stabilities of SiN clusters (N≤24) on Ag(111)surface as the initial stage of epitaxial growth of silicene and three types of silicene superstructures on Ag(111) surface. Analysis reveals p-d hybridization between Ag and Si as well as sp2characteristics in SiN@Ag(111), without dome-shaped configuration. Molecular dynamic simulation shows high thermal stability of silicene monolayer on Ag(111) surfaces, contrast to that on Rh(111) surface. The superiority of Ag substrate for silicene growth is explained, which would be helpful for improving the experimentally epitaxial growth of silicene. |
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