Patterning Charge States on 2D Materials by van der Waals Assembly Stacking

在过去的几十年里，人们对低维纳米结构的科学和技术兴趣显著增长，碳纳米管和石墨烯对这一进展起到了核心作用。尽管观察到在将这种纳米结构集成到有用的设备中取得了重大进展，但在大规模使用之前，对其电子性质的控制仍然是一个主要限制。人们对电子性质从导体(石墨烯)到绝缘体(六方氮化硼，h-BN)和半导体(黑磷，BP和过渡金属二卤化物，TMD)的更大类别的2D材料也越来越感兴趣。然而，即使考虑到用于调制带隙数值和传输载流子数量的不同方法，对于这些2D材料来说，仍然缺乏对电子性质的控制。这一限制对技术的发展产生了巨大的影响，但计算模型的支持对指导实验工作是非常有益的。*我们建议研究一种有希望的方法来改变2D材料的电子性质，即自组装网络的物理吸附。我们将考虑范德华(VDW)异质结构，这种异质结构是由吸附在石墨烯、h-BN等有前景的2D材料上的分子纳米孔组装而成的。分子组装在这种VDW异质结构中的目标作用是调节和控制2D材料的电子性质，以期发现和实现新的功能。一种功能是利用分子组装的形状，在分子构建单元上嫁接的给体/受体(D/A)基团的帮助下，在表面上印记电荷掺杂图案。按照这种方法，具有特定电子性质的原始材料的区域将被雕刻在衬底上，这些区域由掺杂区很好地划定。D/A组的选择将以它们调制2D材料中的电荷掺杂的能力为指导。我们的主要目标是控制整个纳米孔网络的形状，包括孔的大小，以及分子组装和2D材料之间电荷转移的性质和大小。为了解决与能带结构工程相关的基本问题，我们将使用第一性原理密度泛函理论(DFT)计算和扫描隧道显微镜(STM)模拟。我们的计算方法将使我们能够揭示VDW异质结构中分子-表面和分子-分子相互作用的基本方面。虽然这种类型的界面的描述在材料科学中非常重要，但电荷调制的基本方面对开发更高效、更高性能的器件的小型但高度可扩展的构建块具有重大影响。

The scientific and technological interests for low-dimensional nanostructure have remarkably grown during the last decades, carbon nanotubes and graphene have played a central role to this progress. Despite the major advancement observed to integrate such nanostructure into useful devices, the control of their electronic properties remains a major limitation before their use at a larger scale. There is also an increasing interest for a larger class of 2D materials in which the electronic properties go from conductor (graphene) to insulators (hexagonal-boron nitride, h-BN), and semiconductor (black phosphorus, bP and transition-metal dichalcogenides, TMD). Nevertheless, the lack of the control of electronic properties remains for those 2D materials, even when considering the different approaches used to modulate the band gap value and the number of transport carriers. This limitation has a dramatic impact on the development of technologies, but where a support from computational modeling can be highly beneficial to guide the experimental efforts.*** ***We are proposing to investigate one promising route to modify the electronic properties of 2D materials, the physisorption of self-assembled networks. We will consider van der Waals (vdW) heterostructures built from a molecular nanoporous assembly adsorbed on promising 2D materials such as graphene, h-BN, and other materials. The targeted role of the molecular assembly in such vdW heterostructures is to modulate and control the electronic properties of the 2D materials with the aim to uncover and implement new functionalities. One functionality would be to capitalize the shape of the molecular assembly to imprint a charge doping pattern on a surface with the help of donors/acceptors (D/A) groups grafted on the molecular building units. Following this approach, domains of pristine materials with specific electronic properties that are well delimited by doped regions will be carved on the substrate. The choice of the D/A group will be guided by their ability to modulate charge doping in the 2D materials. Our main objectives aimed at controlling the overall nanoporous network shape including the size of the pores, but also on the nature and magnitude of the charge transfer between the molecular assembly and the 2D materials. To address the fundamental issue related to band structure engineering, we will use first principles density functional theory (DFT) calculations and scanning tunneling microscopy (STM) simulations. Our computational approach will allow us to reveal the fundamental aspects of molecule-surface and molecule-molecule interactions within the vdW heterostructures. Although the description of this type of interface is of primary importance in material science, the fundamental aspects of the charge modulation have a major impact to develop small but highly scalable building blocks for more efficient high performance devices.