The backside of graphene: functionalization by intercalation

作为原子层材料，石墨烯的原子同时是正面和背面表面原子。因此，石墨烯的性质在很大程度上取决于其环境。只有当两侧都被真空束缚时，它的性质才接近纯悬浮物质的理论预测。然而，石墨烯通过与其他材料接触而受到影响的容易性是其独特的特征之一，并定义了其应用潜力的组成部分。在这个提议中，我们将使用插层，在石墨烯的背面和它的衬底之间插入原子层，作为一种工具来改变它的属性及其与正面环境的相互作用。这些研究将依赖于一种全原位表面科学方法来生长、修饰和分析结构完美的石墨烯。通过定义明确的实验，明确的理论建模将是可能的。嵌入提供了一种灵活的手段，大大改变狄拉克电子的化学势，提供了一个更大的数量级的变化，可通过外部门控。作为我们研究的一个特定工具，我们将使用嵌入模式提供了一个强大的局部变化的掺杂水平。我们将探讨极端的p-和n-掺杂如何改变离子吸附物，有机分子和自由基与石墨烯的化学相互作用的性质。新的，迄今未观察到的现象，在石墨烯中，如掺杂依赖的分子开关，掺杂依赖的有序吸附原子，或写入的化学图案预定的嵌入模式。石墨烯已被证明是一种优良的自旋导体。如果能够在石墨烯中诱导自旋极化，自旋电子学的应用潜力将大大增加。这种观点已经引发了大量的努力，通过与铁磁3d材料接触来诱导自旋分裂狄拉克锥。然而，石墨烯的d电子与π电子系统的强杂化似乎限制了这一概念的适用性。为了实现自旋分裂和完整的狄拉克锥，我们在这里探索使用到目前为止尚未研究的稀土金属夹层，也结合铁磁层。

As atomic layer material, the atoms of graphene are at the same time front- and backside surface atoms. Therefore, the properties of graphene depend crucially on its environment. Only if bounded on both sides by vacuum, its properties come close to the theoretical predictions for the pure, suspended material. However, the ease by which graphene is affected through contact with other materials is one of its unique features and defines an integral part of its potential for applications. In this proposal we will use intercalation, the insertion of atomic layers in between the backside of graphene and its substrate, as a tool to change its properties and its interaction with the environment on its frontside. The investigations will rely on an all in situ surface science approach to grow, modify and analyze structurally perfect graphene. Through well-defined experiments unambiguous theoretical modeling will be possible.Intercalation provides a flexible means to drastically modify the chemical potential of the Dirac electrons, providing changes an order of magnitude larger as available by external gating. As a specific tool for our research, we will use intercalation patterns providing a strong local variation of the doping level. We will explore how extreme p- and n-doping changes the nature of the chemical interaction of ionic adsorbates, organic molecules and radicals with graphene. New, hitherto unobserved phenomena in graphene are expected, such as a doping dependent molecular switching, doping dependent ordering of adatoms, or writing of chemical patterns predefined by intercalation patterns. Graphene has been proven to be an excellent spin conductor. The application potential for spintronics would greatly increase, if it would be possible to induce spin polarization in graphene. This perspective has already triggered a large effort to induce a spin-split Dirac cone through contact with ferromagnetic 3d materials. However, the strong hybridization of the d-electrons with the pi-electronic system of graphene appears to limit the applicability of this concept. To achieve a spin-split and intact Dirac cone, we explore here the use of up now uninvestigated rare earth metal intercalation layers, also in combination with ferromagnetic layers.