Local Atomic and Electronic Structure

FunCOS-1项目旨在原子尺度上研究分子在氧化物表面的吸附、自组装和共价网络的形成。为此，在超高真空条件下，利用低温扫描隧道显微镜和非接触原子力显微镜，将分子沉积在CoO、Co3O4和MgO表面，并在原子尺度上研究其吸附行为和自组装行为。FunCOS 1将通过选择分子侧基和激活尚未在氧化物上研究的分子间结合方案，进一步发展分子自组装的方向。羧基和氨基之间的氢键、卤素的成键以及氧化物表面金属配位网络的形成是人们最感兴趣的。研究了官能团和金属原子在氧化物上的热稳定性。与官能团的活化有关的是分子的表面反应引入的对分子-底物相互作用的其他修饰。一个突出的例子是在第一个FunCOS资助期内在MgO和CoO上发现的游离基卟啉的自我金属化。有迹象表明，在自金属化过程中释放的氢可能会导致CoO表面结构的变化，影响分子的吸附和自组装。因此，本项目将详细研究氧化钴和氧化镁表面的氢和羟基的性质。这将通过故意分别由原子源提供氢原子或羟基或通过水的解离来实现。此外，还将研究氧化物表面上分子间的脱氢或脱卤化同质偶联以及利用金属有机键形成共价网络的问题。探索氧化物表面功能化的可能性将通过研究原子尺度缺陷在触发甚至催化适当的表面反应中的作用来进行，原子尺度缺陷是自然发生的或由离子或电子辐照产生的。最后，将使用扫描探针光谱来确定分子体系的电子性质。通过扫描隧道谱研究了分子前线轨道和分子-氧化物界面的能级排列。通过开尔文探针力显微镜，将研究分子层内和分子-氧化物界面上的局部接触电势差异。该项目的活动很好地嵌入了FunCOS研究单位的活动。局域观点补充了其他FunCOS项目中使用的非局域电子能谱和散射方法对分子吸附的研究。将与FunCOS 6合作，设计扫描探头结果的理论模型。

The project funCOS 1 aims at investigating molecular adsorption, self-assembly and covalent network formation on oxide surfaces at the atomic scale. For that it employs low-temperature Scanning Tunneling Microscopy and non-contact Atomic Force Microscopy in ultra-high vacuum.Molecules from the funCOS molecular toolbox will be deposited on CoO, Co3O4, and MgO surfaces and their adsorption behavior and self-assembly will be studied at the atomic scale. FunCOS 1 will further develop the steering of molecular self-assembly by the choice of molecular side-groups and by activating intermolecular binding schemes that are not yet investigated on oxides. The hydrogen bonding between carboxyl and amino groups, halogen bonding and the formation metal-coordinated networks on oxide surfaces is of prime interest. The thermal stability of the functional groups and metal adatoms on oxides will be investigated.Related to the activation of functional groups are other modifications of the molecule-substrate interaction introduced by on-surface reactions of the molecules. A prominent example is the self-self-metalation of free-base porphyrins found on MgO and CoO during the first funCOS funding period. There are hints that hydrogen released during self-metalation might induce structural changes on CoO influencing molecular adsorption and self-assembly. This project will therefore study in detail the properties of hydrogen and hydroxyls on cobalt oxide and magnesium oxide surfaces. This will be achieved by intentionally supplying hydrogen atoms or hydroxyls by an atom source or by the dissociation of water respectively. Further, dehydrogenative or dehalogenated homocoupling between molecules, and the formation of covalent networks employing metalorganic bonds will be studied on oxide surfaces. The potential of functionalizing oxide surfaces will be explored by investigating the role of atomic-scale defects, naturally occurring or created by ion or electron irradiation, in triggering or even catalyzing appropriate surface reactions. Finally, scanning probe spectroscopies will be used to determine the electronic properties of the molecular systems. By Scanning Tunneling Spectroscopy molecular frontier orbitals and the energy-level alignment at the molecule-oxide interface will be studied. By Kelvin Probe Force Microscopy local contact potential differences within molecular layers and across the molecule-oxide interface will be investigated.The activities of this project are well embedded within the activities of the funCOS research unit. The local view complements the studies of molecular adsorption by non-local electron spectroscopy and scattering methods employed in the other funCOS projects. In collaboration with funCOS 6 a theoretical modeling of the scanning probe results will be devised.