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一起。通过这种方式，可以制造出所谓的范德华异质结构，其名称源于层间键合的类型。由于每一层只有一个或几个原子厚，因此逐层组装提供了对一维材料结构的基本原子分辨率控制。与此同时，尽管可以使用聚焦的电子或离子束以高分辨率对二维材料的各个层进行图像化，但相比之下，对异质结构中每个平面内材料形态的空间控制迄今为止非常有限。在这个项目中，我们将探索一种全新的方式来将物质排列成任意的3D形状。我们将把纳米级结构与现代（扫描）透射电子显微镜或聚焦离子束仪器结合起来，将二维材料逐层组装起来。通过将预先结构化的二维材料层堆叠在一起，原则上可以获得任意的三维几何形状。这是3D打印的概念，其中一层一层地构建结构，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/图案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和层与层之间的相互作用来定制材料的性能。为此，我们将使用透射电子显微镜和光谱学、拉曼光谱和其他光学方法以及输运实验来广泛表征所得结构。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合理化。这些模拟也有助于选择纳米结构的最佳参数。总的来说，该项目将允许开发一类新的材料，定制材料特性的新方法，并将为纳米级设备的工程开辟新的路线。

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.