Self-assembled structures of hexa-tert-butyl-hexa-peri-hexabenzocoronene (HB-HBC) on the Si(111)-$\sqrt{3}\times \sqrt{3}$-Ag surface have been investigated by low-energy electron diffraction and low-temperature scanning tunneling microscopy (STM). The HB-HBC molecules are assembled into a $\sqrt{21}\times \sqrt{21}-$R$\pm 10.9^{\circ }$ structure with respect to the Si(111)-$1\times 1$ surface. Although the periodic structure is unchanged as a function of molecular coverage, we find that the orientations and adsorption sites of HB-HBC within the molecular islands are changed at near a full monolayer. At submonolayer coverages, the tert-butyl groups of HB-HBC are adsorbed on both the Si and Ag trimers of the Si(111)-Ag surface, and only on the Si trimers at a full monolayer. This result should be associated with a balance between substrate-molecule and inter-molecule interactions.

六的自组装结构叔丁基六围-hexabenzocoronene（HB-HBC）在Si（111） -$\sqrt{3}\times \sqrt{3}$-Ag 表面已通过低能电子衍射和低温扫描隧道显微镜 (STM) 进行了研究。HB-HBC 分子组装成一个$\sqrt{21}\times \sqrt{21}-$电阻$\pm 10.9^{\circ }$ 结构相对于 Si(111)-$1\times 1$表面。尽管周期性结构作为分子覆盖度的函数没有改变，但我们发现分子岛内 HB-HBC 的取向和吸附位点在接近完整的单层时发生了变化。在亚单层覆盖范围内，HB-HBC的叔丁基被吸附在 Si(111)-Ag 表面的 Si 和 Ag 三聚体上，并且仅吸附在全单层的 Si 三聚体上。这一结果应该与底物-分子和分子间相互作用之间的平衡有关。