A New Versatile Production Method for Energy Applications Based on 2D Materials

July 06, 2020 by Luke James

Researchers at the University of Essex in the UK have pioneered a new production method for heterostructure devices, based on two-dimensional (2D) materials like graphene.

High-quality van der Waals heterostructures are produced by stacking together different 2D materials. With highly customizable properties, they have many potential applications and advantages compared with conventional semiconductor heterostructure devices. 

To fully exploit van der Waals materials and their vertically stacked heterostructures, however, we need new mass-scalable production routes that are both low cost and able to preserve the high electronic and optical qualities of the single crystals.

Currently, van der Waals heterostructures are constructed via mechanical exfoliation of bulk single crystals, built up later-by-layer by standard mechanical transfer procedures. However, this is extremely time-consuming and cannot easily be scaled. 

A research team from the University of Essex in the UK has reportedly pioneered a new production method for heterostructure devices. The new study focuses on a production method, based around mechanical abrasion, where multilayer structures are formed through directly abrading different Van der Waals material powders directly on top of one another.


The New Technique

The team's new technique reportedly saw a sharp heterointerface emerge for certain heterostructure combinations. Their results pave the way for a wide range of heterointerface-based devices and other applications to be realized and brought to market. 

To demonstrate their method and its applicability, the research team demonstrated a multitude of different functional devices. These included components commonly found in electronics such as diodes, resistors, capacitors, transistors, and photovoltaics. They also demonstrated the use of these films for energy applications, such as a catalyst in the hydrogen evolution reaction. 

"The production method is really simple, you can go from bare substrate to functional heterostructure device within about 10 minutes. This is all without the need for complex growth conditions, 20 hours of ultra-sonication or messy liquid phase production," said Darren Nutting, co-author of the team's study. 


A graphic showing the production method for heterostructure devices based on 2D materials.

University of Exeter researchers have developed a pioneering production method for heterostructure devices, based on 2D materials such as graphene. Image credited to the University of Essex, Darren Nutting, et al.


Applicable to "Any" 2D Material Crystal

According to Nutting, the team's method applies to any 2D material crystal and can easily be automated to produce heterostructures of random size and complexity. "This allows for the production of a plethora of device possibilities with superior performance to those created using more complex methods," he added. 

Dr. Freddie Withers, also from the University of Exeter and lead author added: "The most interesting and surprising aspect of this work is that sharply defined heterointerfaces can be realized through direct abrasion, which we initially expected would lead to an intermixing of materials when directly abrading layer by layer." 

This is interesting because this observation allows for a large number of different devices to be realized through a simple and low-cost fabrication process potentially. The research team believes that the production method will allow for the rapid up-scaling of heterostructure devices, which could lead to the successful creation of more complex vertical heterostructure devices such as multilayer photovoltaics.