Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime.
Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime.
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DOI：
10.1021/acs.langmuir.5b04069
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发表时间：
2016-02
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影响因子：
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通讯作者：
T. Kirchhuebel;M. Gruenewald;F. Sojka;S. Kera;F. Bussolotti;T. Ueba;N. Ueno;G. Rouillé;R. Forker;T. Fritz
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文献类型：
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作者：
T. Kirchhuebel;M. Gruenewald;F. Sojka;S. Kera;F. Bussolotti;T. Ueba;N. Ueno;G. Rouillé;R. Forker;T. Fritz
四苯基二苯并芘（DBP）是一种很有前途的高效有机光伏电池和有机发光二极管的候选成分。利用互补技术研究了这种特殊的着陆器型分子在Ag（111）上的薄膜结构特性。得到了高度有序的结构，并用低能电子衍射（LEED）对其相互排列进行了表征。扫描隧道显微镜（STM）图像显示在第一单层（ML）中有两种略有不同的排列，都可以描述为特定的人字形模式，每个单元细胞有两个分子，其二苯并芘框架与表面平行。相比之下，第二个ML中的单个DBP分子具有更高的分子内分辨率成像，类似于通过密度泛函数理论（DFT）计算的气相前沿轨道的形状。进一步沉积导致在第一个ML上生长高度有序的双层岛，它们具有相同的单位细胞尺寸和方向，但分子略有倾斜。这表明第一个ML作为进一步层外延生长的模板。同时，大量的第二层分子主要位于台阶边缘或分散在狭窄的梯田上，不能形成高度有序的聚集体。
Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates.