An international team of researchers have shown how to safely integrate fragile 2D materials into optical and electronic devices in a breakthrough that could help further the next generation of devices with applications in high-performance computing, sensing, and flexible electronics.

 

Heterostructures developed by integrating semiconductor and insulating layers are crucial building blocks of electronic devices, and previously this was enabled by bonding a 2D material to an intermediate layer before using it to transfer the 2D material onto the insulator, with the intermediate layer removed with damaging chemicals or high temperatures.

 

However, as reported in Nature Electronics [Satterthwaite et al. Nat. Electron. (2023) DOI: 10.1038/s41928-023-01079-8], here chemical glues or high temperatures were avoided by integrating 2D materials into devices in a single step while also ensuring the surfaces of the materials and the resulting interfaces were kept clean and defect-free.

 

This was achieved using engineering surface forces available at the nanoscale so that the 2D material could be physically stacked onto other prebuilt device layers. As the 2D material is undamaged in the process, it is possible to take advantage of its unique optical and electrical properties.

 

These functionalities required clean interfaces held together by van der Waals forces, special forces that exist between all matter. However, van der Waals integration of materials into fully functional devices are fundamentally limited as they cannot be easily tuned, so some materials cannot be directly integrated with each other just by these interactions.

 

Here the low-adhesion insulator was embedded in a high-adhesion matrix, which helps the 2D material stick to the low-adhesion surface, providing the necessary forces for a van der Waals interface between the 2D material and the insulator. As senior author Farnaz Niroui said “We have come up with a platform to address this limit to help make van der Waals integration more versatile, to promote the development of 2D-materials-based devices with new and improved functionalities.”

 

For electronic devices, a hybrid surface of metals and insulators was formed on a carrier substrate with the surface being peeled off and turned over to offer a smooth, gapless top surface containing the building blocks of the desired device. A 2D material was then prepared in a completely clean environment, and then brought into direct contact with the device stack. When the hybrid surface is in contact with the 2D layer, it can pick up the 2D layer and integrate it with the surface.

 

The team hope to build on this platform to allow integration of many 2D materials to investigate their intrinsic properties without the issue of processing damage, and to produce new device platforms that leverage these functionalities.

“We have come up with a platform to address this limit to help make van der Waals integration more versatile, to promote the development of 2D-materials-based devices with new and improved functionalities.”Farnaz Niroui