Adsorption and two-dimensional phases of a large polar molecule:: Sub-phthalocyanine on Ag(111) -: art. no. 115410
Adsorption and two-dimensional phases of a large polar molecule:: Sub-phthalocyanine on Ag(111) -: art. no. 115410
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DOI：
10.1103/physrevb.68.115410
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发表时间：
2003-09-15
影响因子：
3.7
通讯作者：
Jung, TA
中科院分区：
文献类型：
--
作者：
Berner, S;de Wild, M;Jung, TA
通过结合扫描隧道显微镜和光电子能谱在室温下详细研究了氯[亚酞菁]硼(III) (SubPc)在Ag(111)上的吸附和二维(2D)有序性。 SubPc 是一种极性、高度对称的分子，由扩展的芳香系统和中心 B-Cl 键组成。当在 Ag(111) 上生长时，SubPc 的第一分子层观察到有趣的相行为。在低覆盖率（低于约 0.2 单层 (ML)）时，存在 2D 晶格气体，而在中等覆盖率（约 0.2-0.5 ML）时，观察到与 2D 晶格气体共存的 2D 凝聚分子岛。在这些浓缩的岛屿中，分子组装成有序的蜂窝状图案。在较高的覆盖度（约 0.5-0.9 ML）下，分子组织成 2D 六方密堆积 (hcp) 图案，与致密的 2D 气相达到平衡。在蜂窝结构和六面体图案中，单个分子以亚分子分辨率成像，提供有关其方向的信息。对于蜂窝状和 hcp 图案，观察到相对于 Ag(111) 基底具有两种不同的上层结构取向的岛。在蜂窝图案的情况下，两个上部结构是对映体的。这些层的手性源于吸附 SubPc 后金属表面对称性的丧失，而分子本身本质上是非手性的。基于不同的光电子能谱实验，我们得出结论，SubPc 分子被吸附在 Ag(111) 上，其 Cl 原子朝向基底，并且分子保持完整。最后，讨论了观察到的二维凝聚相和热力学相行为的几个方面，涉及 SubPc 分子的电荷分布和吸附物理和化学。
The adsorption and the two-dimensional (2D) ordering of chloro[subphthalocyaninato]boron(III) (SubPc) on Ag(111) has been studied in detail by combined scanning tunneling microscopy and photoelectron spectroscopy at room temperature. SubPc is a polar, highly symmetric molecule, consisting of an extended aromatic system and a central B-Cl bond. When growing on Ag(111) an interesting phase behavior is observed for the first molecular layer of SubPc. At low coverage, below approximate to0.2 monolayer (ML), a 2D lattice gas is present, whereas at medium coverage (on the order of 0.2-0.5 ML), 2D condensed molecular islands are observed in coexistence with the 2D lattice gas. In these condensed islands, the molecules assemble into a well-ordered honeycomb pattern. At higher coverage (approximately 0.5-0.9 ML) the molecules organize into a 2D hexagonal close-packed (hcp) pattern, in equilibrium with a dense 2D gas phase. In the honeycomb and in the hcp pattern, individual molecules are imaged with submolecular resolution, giving information on their orientation. For both the honeycomb and hcp patterns, islands with two different orientations of the superstructures with respect to the Ag(111) substrate are observed. In case of the honeycomb pattern, the two superstructures are enantiomorphic. The chirality of these layers originates in the loss of the symmetry of the metal surface upon adsorption of SubPc, while the molecules alone are intrinsically achiral. Based on different photoelectron spectroscopy experiments we conclude that the SubPc molecule is adsorbed on Ag(111) with its Cl atom towards the substrate and that the molecule remains intact. Finally, several aspects of the observed 2D condensed phases and the thermodynamic phase behavior are discussed with respect to the charge distribution and the adsorption physics and chemistry of the SubPc molecules.