Hybridization of Organic Molecules with Metal Substrates in the Presence of Surface Passivation Layers

以平铺方式吸附在金属表面上的芳香族分子倾向于与底物电子偶联，即发生金属底物与分子状态的杂化。从基础和基于应用程序的角度来看，控制电子耦合（或解耦）的程度是非常可取的，因为它控制着接口的重要属性。以往文献的研究主要是测量键合强度（可行，例如用TDS），并将吸附表征为（主要）化学吸附或（主要）物理吸附。相比之下，这里提出的项目努力超越这种现有的二元分类。事实上，我们并不想测量任何整体的键合强度，而是详细研究杂化对分子吸附剂的单个电子状态的影响，包括研究中的占据和未占据状态。这将通过选择互补的研究方法（EELS， IETS, STS ARUPS）来完成。虽然从理论上讲，各个状态与底物的相互作用是不同的（参见，例如，电荷回馈的概念），但详细的实验研究很少。特别令人感兴趣的是杂化对电子跃迁的影响的研究，这应该通过微分反射光谱（DRS）来进行：申请人以前的各种工作表明，根据相互作用的类型，在各种底物上观察到第一层有机分子的不同拓宽的吸收光谱，其形状从单体（与溶剂光谱相似）到大大拓宽甚至无结构不等。从原始DRS数据中提取复介电函数，可以直接比较同一分子和同一分子在不同表面上的吸收光谱。通过包含选定的模型分子，我们想尝试推导出金属分子态杂交的广义规则。实验上，我们将通过采用不同的钝化层来改变杂化的程度。我们将重点关注石墨烯和六方氮化硼（h-BN）。我们将进一步考虑用苯基间隔基团使芳分子骨架与表面解耦。在这里，我们将集中讨论二苯并四苯基邻氟蒽（DBP），因为它已经发展成为有机光伏器件（opvd）和有机发光二极管（oled）中应用的有前途的材料。更进一步，更雄心勃勃的项目目标是基于我们的光谱信息，特别是对光谱形状和光谱展宽的分析，推导出杂交程度的定量度量（品质图）。

Aromatic molecules adsorbed in a flat-lying manner on metal surfaces tend to couple electronically to the substrate, i.e., a hybridization of metal substrate and molecular states occurs. Controlling the degree of electronic coupling (or decoupling) is highly desirable from both a fundamental and an application-based point of view, as it governs important properties of the interface.Previous research in the literature mainly aims at measuring the bonding strength (feasible, e.g., with TDS), and to characterize the adsorption as (mostly) chemisorbed or (mostly) physisorbed. In contrast, the project proposed here strives for going beyond this existing binary categorization. In fact, we do not want to measure any integral bonding strength, but examine in detail the impact the hybridization has on the individual electronic states of molecular adsorbates, including both occupied and unoccupied states in the investigation. This will be accomplished by the selection of complementary research methods (EELS, IETS, STS ARUPS). While it has long been known theoretically that individual states interact differently with the substrate (see, e.g., the concept of charge back donation), detailed experimental studies are scarce. Of particular interest is the study of the influence of hybridization on electronic transitions, which should take place by means of Differential Reflectance Spectroscopy (DRS): diverse previous work of the applicant have shown that on various substrates differently broadened absorption spectra of the first monolayer of organic molecules are observed, ranging in shape from monomer-like (being similar to solvent spectra) to greatly broadened and even structureless, depending on the type of interaction. A direct comparison of the absorption spectra of one and the same molecule on different surfaces is feasible by the extraction of the complex dielectric function from the primary DRS data.By inclusion of selected model molecules we want to attempt to derive generalized rules for the hybridization of molecular states on metals. Experimentally, we will vary the degree of hybridization by employing different passivation layers. We will focus on graphene and hexagonal boron nitride (h-BN). We will further consider decoupling of aromatic molecular backbones from surfaces by using phenyl spacer groups. Here, we will concentrate on dibenzotetraphenylperiflanthene (DBP) since it has evolved as a promising material for applications in organic photovoltaic devices (OPVDs) and organic light emitting diodes (OLEDs).A further, even more ambitious project goal is to derive a quantitative measure (figure-of-merit) for the degree of hybridization based on our spectral information, especially on an analysis of the spectral shape and the spectral broadening of the optical spectra.