Van der Waals heterostructures are assemblies of atomically thin 2D crystalline materials that display attractive conduction properties for use in advanced electronic devices.
A representative 2D semiconductor is graphene, but the development of van der Waals heterostructures has been restricted by the complicated and time-consuming manual operations required to produce them. That is, the 2D crystals typically obtained by exfoliation of a bulk material need to be manually identified, collected, and then stacked by a researcher to form a van der Waals heterostructure.
The research team, led by the Institute of Industrial Science at The University of Tokyo, believes its robot will overcome this issue. It comprises an automated, high-speed optical microscope that detects crystals, the positions and parameters of which are then recorded in a computer database. Customised software is used to design heterostructures using the information in the database, the researchers explain. The heterostructure is then assembled layer by layer, by a robotic equipment directed by the designed computer algorithm.
"The robot can find, collect, and assemble 2D crystals in a glove box," first author, Satoru Masubuchi says. "It can detect 400 graphene flakes an hour, which is much faster than the rate achieved by manual operations."
When the robot was used to assemble graphene flakes into van der Waals heterostructures, the team says it was able to stack up to 4 layers an hour, with just a few minutes of human input required for each layer.
The robot was used to produce a van der Waals heterostructure consisting of 29 alternating layers of graphene and hexagonal boron nitride. According to the team, the record layer number of a van der Waals heterostructure produced by manual operations is 13.
"A wide range of materials can be collected and assembled using our robot," co-author, Tomoki Machida explains. "This system provides the potential to fully explore van der Waals heterostructures."
The hope is that the development of this robot will greatly facilitate production of van der Waals heterostructures and their use in electronic devices, and take us a step closer to realising devices containing atomic-level designer materials.
