Image of 2-D material is graphene.
One such 2-D material is graphene, which is comprised of a honeycomb-shaped structure of carbon atoms just one atom thick. (Photo credit: University of Exeter)

The quest to develop microelectronic devices with increasingly smaller size, which underpins the progress of the global semiconductor industry has been stymied by quantum mechanical effects. In order to continue scaling devices ever smaller, researchers are looking at replacing conventional insulators with high-dielectric-constant (high-k) oxides. However, commonly used high-k oxide deposition methods are not directly compatible with 2D materials.

New research outlines a method to embed a multi-functional, nanoscaled high-K oxide within van der Waals devices without degrading the properties of the neighboring 2D materials. A team of engineering experts at the University of Exeter (UK) has pioneered a new way to ease production of van der Waals heterostructures with high-K dielectric-assemblies of atomically thin two-dimensional (2-D) crystalline materials. One such 2-D material is graphene, which is comprised of a honeycomb-shaped structure of carbon atoms just one atom thick. While the advantages of van der Waals heterostructures are well documented, their development has been restricted by complicated production methods.

Now, the research team has 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 laser-writable high-K oxide dielectric into various van der Waals heterostructure devices without damaging the neighboring 2D monolayer materials. This could pave the way for a new generation of flexible fundamental electronic components. The new technique allows for the creation of a host of fundamental nano-electronic and opto-electronic devices including dual gated graphene transistors, vertical light emitting and detecting tunnelling transistors, field effect transistors, memories, photodetectors, and LEDs that operate in the 1 – 2 Volt range.

According to the researchers, the fact they start with a layered 2D semiconductor and convert it chemically to its oxide using laser irradiation allows for high quality interfaces that improve device performance. It’s especially interesting that this oxidation process of the parent HfS2 takes 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.

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