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

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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.