College of Optical and Electronic Technology, China Jiliang University, 310018 Hangzhou, China.
Phys Chem Chem Phys. 2014 Jan 7;16(1):304-10. doi: 10.1039/c3cp53933d.
The structural evolution of planar Si clusters and the nucleation mechanism of silicene in the initial stages of silicene epitaxial growth on a Ag(111) surface are studied by using ab initio calculations and two-dimensional nucleation theory. The ground-state SiN clusters (1 ≤ N ≤ 25) on the Ag(111) surface are found to undergo a significant structural transition from non-hexagonal plane structures to fully-hexagonal ones at N = 22, which is a crucial step for growing a high-quality silicene nanosheet. Furthermore, important parameters for controlling silicene growth, including the diffusion barriers of Si clusters, nucleation barrier, nucleus size, and nucleation rate are explored. Compared to graphene nucleation on transition-metal (TM) surfaces, the low diffusion barrier of Si atoms and the low nucleation barrier are responsible for the rapid nucleation of silicene on a Ag(111) surface. Our calculations demonstrate that silicene should be synthesized at a relatively low growth temperature (~500 K) in order to reduce the defect density. The results can be successfully applied to explain the broad experimental observations where the growth temperature of silicene is below 550 K.
采用第一性原理计算和二维形核理论研究了 Ag(111)表面外延生长硅烯初期平面 Si 团簇的结构演变和硅烯成核机制。在 Ag(111)表面上，基态 SiN 团簇（1≤N≤25）经历了从非六边形平面结构到完全六边形结构的显著结构转变，这是生长高质量硅烯纳米片的关键步骤。此外，还探讨了控制硅烯生长的重要参数，包括 Si 团簇的扩散势垒、形核势垒、核大小和形核速率。与过渡金属（TM）表面上的石墨烯形核相比，Si 原子的低扩散势垒和低形核势垒是硅烯在 Ag(111)表面上快速形核的原因。我们的计算表明，为了降低缺陷密度，硅烯的合成温度应该相对较低（约 500 K）。该结果可成功应用于解释广泛的实验观察结果，即硅烯的生长温度低于 550 K。
