What graphene is
Graphene is a single layer of carbon atoms arranged in a flat, repeating hexagonal pattern, like a microscopic chicken-wire fence. It is one atom thick. Stack many such layers loosely on top of each other and you get graphite, the soft, gray material in graphite pencils.
The title of this article describes graphene as “superconducting and superstrong.” Only part of that is accurate, so it helps to be clear at the start. Graphene is very strong for its thickness, and it conducts electricity well. Ordinary graphene is not a superconductor, though. Superconductivity, the flow of current with no electrical resistance, has been reported only in specially prepared forms, and only at extremely low temperatures. That is covered below.
Theory came first
Physicists were writing about single layers of graphite long before anyone had one in hand. In 1947, the physicist Philip Russell Wallace calculated the electronic structure of a single graphite layer as a stepping stone toward understanding bulk graphite. His results suggested that electrons in such a layer would behave in an unusual way. He was working on paper, and a real isolated sheet was not part of his goal.
Over the following decades, many researchers took the opposite view: a perfectly flat, one-atom-thick crystal should not be stable. Heat, they argued, would make it crumple or fall apart. So single layers were treated mostly as a theoretical building block, useful for modeling graphite, nanotubes and other carbon structures.
Meanwhile, chemists made related discoveries. In 1962, Hanns-Peter Boehm and colleagues reported very thin carbon flakes made from graphite oxide, and later work by Boehm’s group proposed the name “graphene” in the 1980s. Fullerenes (soccer-ball-shaped carbon molecules) were reported in 1985, and carbon nanotubes drew wide attention after Sumio Iijima’s 1991 report. Both can be thought of as graphene sheets rolled or wrapped into new shapes, so interest in the flat sheet itself kept growing.
The 2004 experiment
In 2004, Andre Geim, Konstantin Novoselov and their colleagues at the University of Manchester published a paper in the journal Science describing electric-field effects in ultrathin carbon films, including single layers. Their method was strikingly simple. They pressed adhesive tape against a piece of graphite, peeled it off, and pressed the tape repeatedly against itself to thin the flakes, then transferred the thinnest flakes to a silicon wafer with an oxide coating. On that surface, single layers could be spotted under an ordinary optical microscope because they change the way light interferes slightly.
Other groups had been working toward thin graphite films too, and some earlier work had produced layers that were thin but not clearly single. The Manchester result is widely regarded as the point at which isolated graphene was identified, measured and shown to respond to an electric field. This mattered because it turned a theoretical object into something any well-equipped lab could study.
The two physicists shared the 2010 Nobel Prize in Physics for what the prize committee described as groundbreaking experiments on the two-dimensional material graphene.
Why the flat sheet surprised people
Two things made graphene stand out once it could be measured.
- It exists. The earlier argument that a flat crystal could not be stable turned out to be too simple. Real graphene sheets are not perfectly flat. They show small ripples, which seem to help keep them stable.
- Electrons move in an unusual way. In graphene, the charge carriers behave as if they have almost no mass, which matches the pattern first calculated by Wallace and others. Experiments also showed odd quantum effects that scientists could observe even at room temperature.
What is well established
Several properties of graphene are measured and widely agreed upon.
- Mechanical strength. For its thickness, graphene is one of the strongest materials measured. Laboratory tests on small, clean samples support this. Sheets used in real products are usually messier, so the headline numbers are not what a finished object will deliver.
- Electrical conduction. Electrons move through good-quality graphene with little scattering. How well this is achieved depends heavily on the sample, the surface underneath it, and impurities.
- Heat conduction. Measurements suggest graphene conducts heat very well, though the exact figures vary between experiments.
- Transparency. A single layer absorbs only a small fraction of passing light, which is why researchers have looked at it for see-through electrodes.
What is hoped for rather than proven
“Wonder material” language has often outrun the evidence. A few points of caution:
- Superconductivity. Pristine graphene is not a superconductor. In 2018, a team at MIT led by Pablo Jarillo-Herrero reported superconducting behavior in two graphene layers stacked and twisted by a particular “magic” angle of about 1.1 degrees. The effect appeared only at temperatures a little above absolute zero. It is an important finding for physics, and it has no direct use for everyday equipment today.
- Mass production of perfect sheets. Tape peeling gives tiny flakes, fine for research but not for industry. Growing large, uniform, defect-free graphene remains a harder engineering problem than early headlines implied.
- Replacing silicon. Graphene lacks a natural gap in its electronic structure, which makes it difficult to switch off like a transistor. That is the heart of the story told in the history of graphene electronics, and it is why graphene has not displaced silicon chips.
- Consumer products. Graphene is used in some composites, coatings, inks and battery additives, and research continues into sensors and flexible displays. Claims on packaging are not always easy to check, and the amount of true single-layer graphene in a product is often small or unspecified.
How to read claims about graphene
Because the 2004 discovery was so recent, the material is still in the stage where results appear in laboratories first and in products slowly, if at all. A useful habit is to ask three questions: was it measured in a lab or in a finished product, was the sample one layer or a thick graphite-like powder, and does the claim name a specific temperature and condition?
Graphene’s story also shows how a material can sit on paper for decades. The theory dates from the 1940s. Related carbon structures were discovered in the 1960s through the 1990s. A clever, low-tech experiment finally gave researchers a sheet they could handle. The long-term impact, including in lithium-ion batteries and flexible touchscreen interfaces, is still being worked out.