Department of Engineering and Physics, Karlstad University, SE-651 88 Karlstad, Sweden.
J Chem Phys. 2018 Oct 28;149(16):164707. doi: 10.1063/1.5053606.
PTCDI molecules were evaporated onto a Ag/Si(111) surface and studied using scanning tunneling microscopy (STM) and angular resolved ultraviolet photoelectron spectroscopy (ARUPS). High resolution STM images are used to identify the delicate molecule/molecule and molecule/substrate interactions and the shapes of the molecular orbitals. The results show that the substrate/molecule interaction strongly modifies the electronic configuration of the molecules as their orbital shapes are quite different at 1 and 2 monolayer (ML) coverage. Simple models of molecular HOMO/LUMO levels and intermolecular hydrogen-bondings have been made for 1 and 2 ML PTCDI coverages to explain the STM images. Changes due to the interaction with the substrate are also found in ARUPS as extra states above the regular HOMO level at 1 ML PTCDI coverage. The ARUPS data also show that the electronic structure of the substrate remains unchanged after the deposition of molecules as the dispersion of the substrate related bands is unchanged. The changes in electronic structure of the molecules are discussed based on a HOMO/LUMO split.
PTCDI 分子被蒸发到 Ag/Si(111) 表面，并使用扫描隧道显微镜 (STM) 和角分辨紫外光电子能谱 (ARUPS) 进行研究。高分辨率 STM 图像用于识别精细的分子/分子和分子/衬底相互作用以及分子轨道的形状。结果表明，衬底/分子相互作用强烈改变了分子的电子构型，因为它们在 1 和 2 单层 (ML) 覆盖时的轨道形状有很大的不同。对于 1 和 2 ML PTCDI 覆盖，已经建立了分子 HOMO/LUMO 能级和分子间氢键的简单模型，以解释 STM 图像。在 1 ML PTCDI 覆盖时，由于与衬底的相互作用，在常规 HOMO 能级上方也会出现额外的状态，在 ARUPS 中也会发现这种变化。ARUPS 数据还表明，在分子沉积后，衬底的电子结构保持不变，因为与衬底相关的能带的色散没有变化。根据 HOMO/LUMO 分裂讨论了分子电子结构的变化。
