In 2004, researchers discovered an ultra-thin material that is at least 100 times stronger than steel and is also best known as a thermoelectric conductor. This means that the material, known as graphene, could lead to faster electronics than silicon.
But to be useful, graphene needs to carry a switching current, as silicon does on computer chips in the form of billions of transistors. This switch mode also creates the strings 0 and 1 that the computer USES to process information.
Then researchers from purdue university, the university of Michigan and huazhong university of science and technology collaborated to show how lasaer pointer technology could permanently strengthen graphene into structures that allow electric currents to flow. This structure is known as a “band gap.” Electrons need to cross this gap to become conducting electrons, which can carry current.
But graphene doesn’t have what’s called a band gap. Purdue university researchers created and expanded the band gap in graphene to a record 2.1 electron volts. To function as a semiconductor, such as silicon, the band gap must reach at least the previously realized record of 0.5 electron volts.
“This is the first time we have achieved such a high band gap without any impact on the graphene itself, such as through chemical doping.” Gary Cheng, a professor of industrial engineering at purdue university. The existence of a band gap allows semiconductor materials to switch between insulation or conducting currents, depending on whether their electrons pass through the band gap.
Achieving 0.5 electron volts could unlock more potential for graphene in next-generation electronic devices, the researchers said.
“Previous researchers only opened the band gap by simply stretching the graphene, but simple stretching does not make the band gap wider. What we need is to permanently change the shape of the graphene to maintain the band gap,” said Cheng. Cheng and his team not only maintained the bandgap in graphene, but also adjusted the bandgap width from zero to 2.1 electron volts, allowing scientists and manufacturers to use certain properties of graphene according to their needs.
The researchers used laser shock imprinting, a technology Cheng developed in 2014 with scientists at Harvard University, the instituto higher learning in Madrid and the university of California, San Diego, to make bandgap structures permanent in graphene.
In the study, the researchers used lasers to create shock waves that penetrate the graphene sheets below; The laser shock then strains the graphene onto a grooved mold and makes it permanent. The band gap can be adjusted by adjusting the laser power.
Cheng said that while the technology is far from being able to integrate graphene into semiconductor devices, it offers greater flexibility in using the optical, magnetic and thermal properties of materials.