Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore.
Phys Chem Chem Phys. 2011 Dec 21;13(47):20933-8. doi: 10.1039/c1cp22769f. Epub 2011 Oct 17.
The epitaxial growth of the 1st and 2nd monolayer (ML) diindenoperylene (DIP) on Ag(111) has been systematically investigated using low temperature scanning tunneling microscopy, low energy electron diffraction and first-principles calculations. At one ML regime, DIP molecules commensurately arrange in either herringbone or brick-wall superstructures, depending on the deposition rate. Tip-induced structural transformation from herringbone to brick-wall is observed. Calculations based on density functional theory reveal that the top site of Ag(111) is energetically favorable for both superstructures. The 2nd ML DIP aggregate in either herringbone or brick-wall superstructures depending on the arrangements of the 1st ML DIP, indicating that the structural properties of DIP thin films on Ag(111) are sensitive to growth conditions. The observed variation in DIP ultrathin film structure may result in different electronic properties and have implications for DIP-based organic electronic devices, such as organic field-effect transistors or organic photovoltaic cells.
采用低温扫描隧道显微镜、低能电子衍射和第一性原理计算系统地研究了苝二酰亚胺（DIP）在 Ag（111）上的第 1 和第 2 单层外延生长。在单层范围内，DIP 分子根据沉积速率以鱼骨型或砖墙型超结构共形排列。观察到从鱼骨型到砖墙型的尖端诱导结构转变。基于密度泛函理论的计算表明，Ag（111）的顶位对于两种超结构都是能量有利的。第 2 层 DIP 在鱼骨型或砖墙型超结构中聚集，具体取决于第 1 层 DIP 的排列，这表明 DIP 在 Ag（111）上的薄膜结构性质对生长条件敏感。观察到的 DIP 超薄薄膜结构的变化可能导致不同的电子性质，并对基于 DIP 的有机电子器件（如有机场效应晶体管或有机光伏电池）具有重要意义。
