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

在过去的几十年里，低维纳米结构的科学和技术兴趣显着增长，碳纳米管和石墨烯在这一进展中发挥了核心作用。尽管观察到将这种纳米结构整合到有用的器件中的重大进展，但在它们以更大规模使用之前，对其电子性质的控制仍然是一个主要的限制。人们对更大类别的2D材料也越来越感兴趣，其中电子性质从导体（石墨烯）到绝缘体（六方氮化硼，h-BN）和半导体（黑磷，bP和过渡金属二硫属化物，TMD）。然而，对于那些2D材料，即使考虑用于调制带隙值和传输载流子数量的不同方法，仍然缺乏对电子特性的控制。这种限制对技术的发展产生了巨大影响，但计算建模的支持对于指导实验工作非常有益。* * 我们建议研究一种有前途的方法来改变2D材料的电子特性，即自组装网络的物理吸附。我们将考虑货车德瓦耳斯（vdW）异质结构从分子纳米多孔组件吸附在有前途的二维材料，如石墨烯，h-BN，和其他材料。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材料的电子特性，目的是发现和实现新的功能。一种功能是利用分子组装体的形状，以在接枝在分子构建单元上的供体/受体（D/A）基团的帮助下在表面上压印电荷掺杂图案。按照这种方法，将在衬底上雕刻具有特定电子特性的原始材料的域，这些域由掺杂区域很好地界定。D/A基团的选择将由它们调节2D材料中的电荷掺杂的能力来指导。我们的主要目标是控制整个纳米多孔网络的形状，包括孔的大小，但也对分子组装和2D材料之间的电荷转移的性质和幅度。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分子-表面和分子-分子之间的相互作用的vdW异质结构内的基本方面。虽然这种类型的接口的描述在材料科学中是首要的，但电荷调制的基本方面对开发用于更高效的高性能器件的小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.