New avenues to nanofabrication: assembly of vertical heterostructures from nanopatterned two-dimensional materials

二维（2D）材料可以以任意顺序堆叠在彼此的顶部上。以这种方式，可以制造所谓的货车德瓦尔斯异质结构，其名称来源于层之间的键合类型。由于每层只有一个或几个原子厚，逐层组装提供了沿沿着一个维度对材料结构的基本原子分辨率控制。同时，尽管可以使用聚焦电子束或离子束以高分辨率对2D材料的各个层进行图案化，但是相比之下，到目前为止，对异质结构中每个平面内的材料形态的空间控制非常有限。在这个项目中，我们将探索一种全新的方式，将物质排列成任意的3D形状。我们将联合收割机与2D材料的逐层组装结合起来，这种纳米级结构已经可以用现代（扫描）透射电子显微镜或聚焦离子束仪器来实现。通过将预结构化的2D材料层放置成堆叠，原则上可以获得任意的3D几何形状。这是3D打印的概念，其中结构是逐层构建的，除了这里的每层只有一个或几个原子厚，并且每层内的结构化/图案化也有望以亚纳米精度实现。在制备独特的新结构方面，我们将特别研究如何通过纳米结构化并结合层间相互作用来定制材料的特性。为了这个目的，我们将广泛地使用透射电子显微镜和光谱，拉曼光谱和其他光学方法，以及传输实验的特点所产生的结构。实验结果将在广泛的最先进的原子模拟和第一性原理计算的帮助下得到合理化。模拟也应该有助于选择最佳参数的纳米结构。总的来说，该项目将允许开发一种新的材料，定制材料特性的新方法，并将为纳米级器件的工程开辟新的途径。

Two-dimensional (2D) materials can be stacked on top of each other in an arbitrary sequence. In this way, so-called van der Waals heterostructures can be manufactured, with the name originating from the type of the bonding between the layers. Since every layer is only one or a few atoms thick, the layer-by-layer assembly provides an essentially atomic-resolution control over the material structure along one dimension. At the same time, although individual layers of 2D materials can be patterned at a high resolution using focused electron or ion beams, spatial control over materials morphology within each plane in heterostructures is, in contrast, very limited so far. Within this project we will explore a fundamentally new way to arrange matter into arbitrary 3D shapes. We will combine the nanoscale structuring that has become possible with modern (scanning) transmission electron microscopes or focused ion beam instruments with the layer- by-layer assembly of 2D materials. By placing pre-structured 2D material layers into a stack, an in principle arbitrary 3D geometry can be obtained. This is the concept of 3D printing, where a structure is built layer by layer, except that here each layer is only one or a few atoms thick and structuring/patterning within each layer is also expected to be possible with sub-nanometer precision. In connection with preparing unique new structures, we will investigate in particular how the properties of the materials can be tailored by the nanostructuring and in combination with the interaction between layers. For this purpose, we will extensively characterize the resulting structures using transmission electron microscopy and spectroscopy, Raman spectroscopy and other optical methods, as well as transport experiments. The experimental results will be rationalized with the help of extensive state-of-the art atomistic simulations and first-principles calculations. The simulations should also help to choose optimum parameters for nanostructuring. Overall, the project will allow to develop a new class of materials, new ways for tailored material properties, and will open new routes to the engineering of nanoscale devices.