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Imagine that you have a road without traffic lights. In this scenario, cars can move freely without stopping, and this is similar to how electrons move in graphene, because it has what is known as the “zero band gap”, and this is a property that is not required.
Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. Although it has extraordinary electrical, thermal and mechanical properties, the need to control the flow of electrons – just like using traffic lights to manage cars – prevented its use in the manufacture of semiconductors used in devices such as “transistors”, and “silicon” has remained a material until now. Dominating this market, because it has a “range gap”, despite its other disadvantages.
For many years, scientists have been seeking to find a band gap in graphene, by adding “traffic lights” that allow a controlled stop-and-go mechanism in electronics. A research team from the Georgia Institute of Technology in America claims that they have succeeded in this, and produced the world's first functional semiconductor made of graphene after overcoming the major obstacle that has plagued graphene research for decades, which made many believe that graphene electronics will never see the light.
How did scientists put a “traffic light” in graphene?
During a study published in the journal “Nature“, The researchers announced the details of their research project, which lasted 10 years and was crowned with success in giving graphene the “band gap” property, that is, enabling it to place a “traffic light” that allows controlling the flow of electricity.
This achievement included the use of the “epitaxial growth” technique to grow graphene on “silicon carbide” chips using special ovens, which led to the production of epitaxial graphene that has a “band gap” characteristic.
Epitaxial growth is a process used in materials science and semiconductor manufacturing to deposit a thin crystalline layer on a substrate in a way that maintains structural alignment between the atoms of the deposited layer and the atoms of the substrate.
This process can be summarized in the following steps:
- Substrate: It is a base material that is often made of silicon or another crystalline material.
- Raw material: Introduction of a primer to prepare a thin layer on a substrate.
- Deposition process: Use techniques such as chemical vapor deposition or molecular beam deposition, to deposit the starting material onto the substrate.
- Alignment with the substrate: The deposited atoms or molecules arrange themselves in a way that reflects the crystalline structure of the substrate, and this alignment is essential to maintain the properties of the substrate in the thin layer.
- Single crystal layer: As deposition continues, a single crystalline layer of material forms over the substrate.
The researchers were able to employ this technique to deposit a layer of graphene in a way that preserves the crystalline structure of the silicon carbide substrate, so that the resulting epitaxial graphene exhibits semi-conducting properties, making it compatible with traditional microelectronics processing methods and suitable for electronic applications.
Faster and more efficient computing
After succeeding in this, the researchers used a technique known as “grafting” to follow the electronic behavior of the new graphene material.
This technique involves introducing specific atoms into graphene, and these atoms “donate” electrons. By adding these electron-donating atoms, researchers can measure the electronic properties of graphene without causing damage to its structure.
The provided atoms allowed the researchers to evaluate whether semiconductor graphene can effectively conduct electricity, which is crucial for its application in electronic devices.
According to the study, graphene semiconductors showed ten times greater mobility than silicon, allowing electrons to move faster with low resistance, making computing faster and more efficient.
This achievement could lead to a qualitative shift in electronics, and graphene may replace silicon in future electronic devices.
Professor Walt de Heer, from the School of Physics at the Georgia Institute of Technology and the study's lead researcher, compares the potential impact of graphene electronics with historical shifts in electronic technologies, such as the move from vacuum tubes to silicon.
De Heer says in statement Journalist released by the Georgia Institute “This achievement we have achieved, represents an important moment in technology akin to the first successful flight of the Wright brothers. They created an airplane that could fly 300 feet in the air, but skeptics asked: Why does the world need to fly when it already has trains and boats?” “Fast? But they insisted, and this was the beginning of the technology with which people could travel across oceans.”
De Heer believes that graphene could represent the next generation of electronics, due to its unique properties that will make computing faster and more efficient.
(See video: Professor Walt de Heer of Georgia Tech's School of Physics tells the story of the achievement)
A starting point towards fast flight
This achievement raises key questions related to the following:
- How did silicon carbide help graphene overcome the challenge of having no band gap, the crucial property necessary to turn semiconductor-based devices on and off?
- How does the method the researchers used to grow graphene on silicon carbide chips differ from previous attempts to create graphene-based semiconductors?
- What limitations does silicon face in the context of modern electronics, prompting the search for alternative materials such as graphene?
- What makes graphene semiconductors unique compared to silicon, especially in terms of their ability to conduct, transfer, and dissipate heat?
- What challenges might graphene face when expanding the idea toward practical use in nanoelectronics?
For its part, Al Jazeera Net presented these questions to Professor De Heer via e-mail, and he indicated in his answer to the first question that the chemical bond of graphene with silicon carbide changes the electronic structure of the former, and gives it the “band gap” required in electronics.
In his answer to the second question, he pointed out that there had been previous attempts to change graphene chemically, for example by interacting with hydrogen, but this led to the emergence of a very poor semiconductor that is not useful for electronics. What distinguishes their achievement is that they achieved properties superior to the most common material, silicon.
In his answer to the third question, he gave three reasons that push the world to try to search for an alternative to silicon, which are:
- Silicone does not help devices be smaller.
- The heat generated in silicone devices becomes too much.
- Processor speeds in silicon devices cannot get higher.
As for the fourth question regarding the advantages of graphene-based semiconductors compared to silicon, he pointed out that graphene is an amazing flat material with strong bonds that we can deal with on the smallest scale, and it can work like a semiconductor or metal, and we can use its unique properties to make fast electronic devices. And thin, and probably better than the ones we currently use with silicone.
Finally, in his answer to the fifth question, he admitted that what they have done is merely a starting point towards an electronic world that is much smaller in size and much faster in performance, stressing that at least a decade of research is needed to produce high-quality commercial nanoelectronics based on graphene.
