Stanene & Its Uses in Integrated Circuits

By Thomas HornigoldMar 26 2018

Table of Contents

Introduction
Stanene as a Topological Insulator
Stanene in Quantum Research
Superconductivity
Conclusion

Introduction

Amongst the wave of 2D materials to be developed in the wake of graphene’s synthesis in 2004, Stanene is one of the most intriguing. In this material, the characteristic hexagonal structure associated with 2D materials consists of atoms of tin. As in the case of other 2D elements, it has mainly been synthesized in the lab by molecular beam epitaxy – deposition of individual particles onto a substrate at conditions of high vacuum and high temperature – and its existence, alongside many of its properties, was determined by theoretical calculations in advance.

Stanene as a Topological Insulator

Stanene is a 2D topological insulator. The topological properties of quantum matter are such an exciting field of research in condensed matter physics, both theoretically and experimentally, that the Nobel Prize in physics was awarded in 2016 to David Thouless, Duncan Haldane and Michael Kosterlitz "for theoretical discoveries of topological phase transitions and topological phases of matter."

Topological insulators can be described as materials that can carry a current – sometimes a superconducting current – on the outside or surface of the device while remaining insulating within the device. The electrons on the edges can travel with practically no resistance whatsoever. This makes them useful for nanoelectronic wiring, and for cases where individual electrons need to be manipulated.

They also have unique properties relating to the spin of the electrons. The electrons that can move along the outside edge of the topological insulator are also insulated from quantum effects that would flip their spin.

2D topological insulators can carry “chiral currents,” where the spins of the electrons are locked into the direction of transport, transferring information. Traditional digital electronics essentially uses the charge on the electron as a means of storing and processing information, so these materials could be invaluable for those who want to use the electron’s spin to encode and transfer information. This opens up a new field: spintronics.

Stanene in Quantum Research

Of course, as well device applications, 2D topological insulators like Stanene are of great interest to theorists. Single atomic layers of stanene exhibit the Quantum Hall effect at room temperature, making them intricate laboratories for the study of quantum matter. Much of the field is devoted to understanding the unusual phenomena where sublime order comes out of the interaction of many particles – such as the manifestation of phase transitions into superconducting states.

Superconductivity

In Nature Physics 2018, it was discovered that stacking multiple layers of Stanene on top of each other could result in a phase transition to superconductivity. As yet, superconductivity in Stanene still occurs at very low transition temperatures, precluding its use over higher-temperature ceramic superconductors or those that are mass-manufactured.  

The hope is that stanene may exhibit many of its unique and useful properties at high temperatures. Scientists from Stanford adopted the “Lego-building-block” approach common to 2D materials studies, where adding individual atoms or additional layer can enhance the desired properties. They noted that by adding atoms of fluorine, the stanene could extend its operating range to over a hundred degrees Celsius, rendering its properties stable over the temperatures likely to be seen in a computer.

With stanene nanowiring, the power consumption and space taken up by electrical current conductors in circuits could be reduced. The result would be faster, more efficient, and smaller integrated circuits. This was the hope of Professor Le Lay, who has worked on 2D materials for many years. Earlier this year, he headed a global research team synthesized planar stanene for the first time, and he was excited about the prospects for this material, saying:

“In the future, we hope to see stanene partnered up with silicene in computer circuitry. That combination could drastically speed up computational efficiency, even compared with the current cutting-edge technology."

Some of the more enthusiastic proponents of stanene suggest that one day, it could displace silicon altogether.

Eventually, we can imagine stanene being used for many more circuit structures, including replacing silicon in the hearts of transistors. Someday we might even call this area Tin Valley rather than Silicon Valley.

Shoucheng Zhang, Stanford - Led research indicating fluorine could be a useful addition to Stanene

Combination

Stanene is one of a class of exciting 2D topological insulators with a unique set of useful electronic properties, and the potential for bizarre, exotic, and useful behavior when used in combination. The extreme energy efficiency that these devices may one day supply is bound to motivate fundamental physics and materials science research into them for years to come – and, one day, integration into the next generation of ultra-fast, ultra-efficient devices.

Thumbnail Image Credit: Anusorn Nakdee/Shutterstock

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