Black phosphorus to take on silicon in electronics boom

Image: Yale University

Black phosphorus, an element that was discovered more than 100 years ago, is beginning to gain interest after researchers discovered the critical role it can play in the future of electronic devices.

Researchers at Yale University, led by Fengnian Xia, Yale’s Barton L. Weller Associate Professor in Engineering and Science, discovered that black phosphorous could potentially replace silicon as the main material for electronics, after the element had previously been sidelined for its lack of use.

At only a few atomic layers thick, the element could deliver a new generation of smaller devices, flexible electronics and faster transistors, the researchers said.

This is due to two key properties; the first is its higher mobility – the speed at which it can carry an electrical charge – compared to silicon and the second is that it has a bandgap. The bandgap gives a material the ability to act as a switch – able to turn on and off in the presence of an electric field and act as a semi conductor. This is in contrast to graphene which has high mobility but no bandgap.

Identifying a way to control the bandgap of black phosphorus is key to unlocking its possible applications.

The researchers found that its bandgap can be controlled at a certain thickness and by applying a vertical electric field to it at that thickness, researchers could ‘tune’ the bandgap, and shrink the moderate gap to a point at which it closes.

This unlocks the possibility of the material to be used in a range of applications including night-vision devices, imaging tools, mid-infrared optical modulators and other optoelectronic technologies.

“Before this study, the bandgap of black phosphorus could not be dynamically tuned, limiting its applications in optoelectronics,” Bingchen Deng, lead author of the study and a Ph.D. student in Xia’s lab, said.

Deng added that having a bandgap that can be controlled means that black phosphorus could potentially be used as a topological insulator, a material with the unusual ability to work as both an insulator (inside the material) and as a conductor (on its surface).

Topological insulators are of high interest to researchers as they could be important for developing low-power electronics.

The black phosphorus research was published in the Nature Communications journal.

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