New technique bends to incorporate high-k dielectrics into 2D heterostructures

"Our method to embed a laser-writable high-k dielectric into various van der Waals heterostructure devices without damaging the neighboring 2D monolayer materials opens doors for future practical flexible van der Waals devices."Freddie Withers, University of Exeter

Researchers at the University of Exeter in the UK have developed an innovative technique that could help create the next generation of everyday flexible electronics. They have pioneered a new way to ease production of van der Waals heterostructures – assemblies of atomically thin, two-dimensional (2D) crystalline materials such as graphene– that contain high-k dielectrics.

While the advantages of van der Waals heterostructures are well documented, their development has been restricted by complicated production methods. The researchers have now developed a new technique that allows these structures to achieve suitable voltage scaling, improved performance and the potential for new, added functionalities by embedding a high-k oxide dielectric in them. This research, which is reported in a paper in Science Advances, could pave the way for a new generation of flexible, fundamental electronic components.

"Our method to embed a laser-writable high-k dielectric into various van der Waals heterostructure devices without damaging the neighboring 2D monolayer materials opens doors for future practical flexible van der Waals devices such as field effect transistors, memories, photodetectors and LED's which operate in the 1–2 Volt range," said Freddie Withers from the University of Exeter and a co-author of the paper.

The quest to shrink microelectronic devices down to increasingly small scales underpins the progress of the global semiconductor industry, but recently this quest has begun to be stymied by quantum mechanical effects. In particular, as the thickness of conventional insulators is reduced, the ease with which electrons can escape from those insulators increases.

In order to continue reducing the scale of microelectronic devices, researchers are looking at replacing conventional insulators with high-dielectric-constant (high-k) oxides such as hafnium dioxide (HfO₂) and hafnium disulfide (HfS₂). However, commonly used high-k oxide deposition methods are not directly compatible with 2D materials.

This latest research outlines a new method for embedding a multi-functional, nanoscaled high-k oxide within van der Waals devices without degrading the properties of the neighboring 2D materials. This new technique allows for the creation of a host of fundamental nano-electronic and opto-electronic devices including dual gated graphene transistors, and vertical light emitting and detecting tunneling transistors.

"The fact we start with a layered 2D semiconductor and convert it chemically to its oxide using laser irradiation allows for high quality interfaces which improve device performance," said Withers. "What's especially interesting for me is we found this oxidation process of the parent HfS₂ to take place under laser irradiation even when it’s sandwiched between two neighboring 2D materials. This indicates that water needs to travel between the interfaces for the reaction to occur."

This story is adapted from material from the University of Exeter, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.