Graphene – the sense of a new world

Author: Geoff Mortimer

Few materials have inspired so many hyperbolic headlines in scientific and industrial fields over the past 20 years as graphene. By the turn of the century, even though scientists knew of the existence of the one atom thick, two-dimensional crystal material, nobody had worked out how to extract it from graphite. Then, in October 2004, two researchers at the University of Manchester, Professors Sir Andre Geim and Sir Konstantin Novoselov, finally made the breakthrough with a paper on “The electric field effect in atomically thin carbon films.” Their ensuing work would ultimately see them awarded with the Nobel Prize for Physics in 2010. 

Ever since, the University of Manchester has been at the forefront of graphene research and development. Thousands of papers have been published, and numerous products and applications have been proposed, ranging from supercomputers and ultra-fast electronics to extra-strong materials. Although some of the more fantastical possibilities for it are yet to materialize, there seems to be little doubt that its influence in the semiconductor sector is set to become ever more considerable, with industries striving for ever-faster, more efficient, and compact electronic devices. Over 50 million graphene-enhanced products are already on the market, providing solutions for products as wide ranging as cars, water filters and solar panels to aircraft  satellites and running shoes.

But what is it about graphene that has sparked such excitement, and what makes it a superior alternative to silicon in the context of semiconductors?

Material of the future 

As well as being the thinnest material in the world, what makes graphene stand out is its phenomenal electron mobility, some 500 times greater than silicon. Because the electrons can move rapidly through its honeycomb-like crystal lattice, it offers faster device performance and improved electrical conductivity. 

In terms of semiconductors, as well as potential advancements in device speed, the use of graphene (and other 2D materials) also shows the potential for flexible electronics, due to its atomically thin nature alongside high mechanical stability and flexibility. Graphene is also a very good thermal conductor which can be a help when looking to further miniaturize device structures.

Professor Geim is currently based at the University of Manchester’s National Graphene Institute (NGI). Established to drive cutting-edge research into graphene and related 2D materials, the NGI has become a global hub for groundbreaking discoveries. Alongside the NGI, the Graphene Engineering Innovation Centre (GEIC) plays a critical role in bridging the gap between academic research and industrial application, fostering collaboration with over 400 companies worldwide.

Since its inception, the GEIC has facilitated the development of over 500 graphene-enhanced projects, from advanced composites to next-generation sensors. These innovations are the result of strategic partnerships and projects designed to translate the extraordinary properties of graphene into real-world solutions. Together, the NGI and GEIC have helped launch over 60 spin-out companies, secured significant investments, solidifying Manchester’s reputation as the “home of graphene”.

Andrew Strudwick, Application Manager for CVD and Printing at the GEIC, explains in an interview with Evertiq, how his team supports these advancements:

"At the GEIC, we provide companies with the tools, expertise, and collaborative environment needed to explore the potential of graphene. Our team works closely with industry partners to prototype and scale next-generation technologies, ensuring graphene moves seamlessly from the lab to impactful commercial applications. This approach is helping to shape the future of electronics, energy, and materials science."

EU backing

In Sweden, the Graphene Flagship was established with similar goals to the GEIC, including the 2D-pilot line, and has gone a long way to proving the worth of this unique material. This EU scientific research initiative was set up in 2013, with a budget of some €1bn and works together with over 100 companies and academic partners in fields ranging from the automotive and aviation to electronics, energy, composites and biomedicine. 

“The project is building on the foundation of the Graphene Flagship Core 3 and 2D-EPL projects,” Inge Asselberghs, 2D-EPL Director and Graphene Flagship Science and Technology Officer, explains to Evertiq. “In the 2D-EPL, the consortium focused on two material classes, graphene and TMDC (MoS2/WS2). Making use of the toolsets available in the consortium and using the new equipment, allowed the growth and transfer modules to mature significantly. Together with the new investments planned in the next 2D-PL project, the goal is to further mature the fabrication processes.

The organization is said to have launched the careers of around 1,000 doctoral and postdoctoral students, and created 20 spin-offs, which have raised a total of more than EUR 170 million in venture capital, filed more than 80 patents, and brought more than 100 products onto the market. According to a report by the research institute WifOR, the Graphene Flagship will have created a total contribution to GDP of €3,800 million and 38,400 new jobs in the 27 EU countries between 2014 and 2030. 

A world of potential 

In terms of semiconductors, the main uses to date for graphene are around sensors, mainly for either gas sensing or bio sensing purposes. Beyond sensors and transistors, the material’s high electrical conductivity and resistance to electro-migration make it ideal for circuit interconnects, reducing energy loss and enhancing performance. From foldable smartphones to wearable technology, graphene’s flexibility and strength are opening up new possibilities for consumer electronics.

A further application comes in the form of Photonics – Graphene’s interaction with light drives innovation in photodetectors, modulators, and other photonic devices, critical for next-generation communication networks

The band gap challenge

The “wonder material” does not come without its challenges, the principle one of which being the so-called “band gap.” 

Essentially, band gaps are energy barriers for the movement of electrons generated within crystal structures due to the symmetries present. In silicon, this energy barrier must be overcome by applying a voltage across the transistor in order for the electrons to flow. The device is therefore “on” when the electrons flow and “off” when they don’t – behavior typical of a semiconductor. 

Graphene behaves as a semi-metal rather than a semi-conductor. The energy barrier preventing electrons from moving in the absence of an external voltage is not present. Therefore, it’s not possible to fully “switch off” the device, which consequently leads to issues around increased power consumption.

Much work has been done to find a solution to the issue over the years including confining graphene into nanoribbons and using alternative device geometries. Another potentially important breakthrough may come via recent work carried out at Tianjin University where researchers have shown a way of forming a graphene material on a silicon carbide substrate that utilizes the interaction at the interface of the two materials to generate a band gap in the resultant film. 

Another issue that still provides a hurdle is scalability and graphene’s integration with existing semiconductor manufacturing. Progress is considerable here too, notably through initiatives like the 2D-Pilot Line, aiming to mature graphene technologies for industrial use, offering prototyping services to bridge the gap between research and application. 

Companies like Paragraf and Graphenea are among many companies producing graphene-based transistors and sensors for commercial testing, but there is still some way to go in this field, according to Graphene Flagship’s Asselberghs. “Graphene bandgap engineering is challenging and requires precise process control. While promising examples are published in literature, significant consideration towards scalability and controllability is essential,” she says. 

Justifiable hype?

All kinds of claims were made about the potential for graphene 20 years ago, some more realistic than others, even then. There are still hurdles to jump, but Inge Isselberghs is confident much more is yet to come, telling Evertiq,

“At the beginning of the Graphene Flagship, people were even skeptical if qualitative graphene can be grown reliably at cm2 scale. Today, we moved already far beyond. The investments made towards wafer level processing and the fabrication of the relevant demonstrators are foundations for evaluation of sensor, photonics and electronics devices,” she says, and in the semiconductor, field alone pushing the boundaries of performance and miniaturization, graphene stands out as a key material driving innovation and providing plenty of cause for optimism. 

Perhaps, as many researchers proclaim, “The graphene revolution has only just begun.”