Advances and opportunities for automated robotic preparation of 2D materials and fabrication of 2D heterostructures
The mechanical exfoliation, transfer, and stacking of 2D atomic sheets from van der Waals crystals synergize to enable atomic layer-by-atomic layer engineering of 2D heterostructures with tailored properties that yield new exotic phenomena and states of matter. With the huge variety of van der Waals materials available, there is a limitless number of ways to couple 2D semiconducting, insulating, magnetic, metallic, topological, etc. systems with one another. Experimental exploration of this vast space starts with the fabrication of high-quality 2D heterostructures, which is commonly performed manually, relying on humans to execute delicate operations. Many scientific advancements have been achieved in this manner, revealing immense potential for further discovery and innovation of increasingly sophisticated 2D heterostructures. However, soon, the complexity of the 2D heterostructures that define the scientific state-of-the-art will exceed the capabilities of manual fabrication. Therefore, the demand for robotic instruments for preparing 2D materials and fabricating complex 2D heterostructures with greater quality, at higher rates, and with better reproducibility is increasing. This review covers recent scientific, instrumentation, and processing advances rising to this challenge. Robotic instruments for mechanical exfoliation, optical metrology of 2D crystallites, stacking, as well as advancements in supporting technologies such as organic-free stamps, vacuum-compatible processing tools, and artificial intelligence (AI) are covered. Looking forward, a new generation of AI-driven, automated advanced manufacturing tools is anticipated to emerge from these current advancements. These new tools will bridge the current state-of-the-art of 2D heterostructure science to new scientific frontiers defined by precision fabrication of high-quality, complex, many-layer 2D heterostructure systems.