Miniscule at just 10 nanometers wide, electronic transistors combine Insulators, semiconductors and metals are combined to form 3D crystals. However, researchers from the Oak Ridge National Laboratory (ORNL) have discovered a may to produce 2D crystals just a nanometer in thickness, opening up possibilities for ultrathin devices.

Researchers from around the world have previously investigated making 2D crystals using common layered materials, constraining electron transport just within two dimensions. It was also revealed earlier that there are ways to pattern single-layer carbon atoms lithographically to create "wires" insulated by a boron nitride layer. Until now, however, there were no methods to process and synthesize junctions of lithographic patterns between two different semiconductors in just one layer a nanometer thick to produce transistors.

ORNL researchers found the way by combining a novel synthesis process with techniques for commercial lithography involving electron beams, creating semiconductor junction arrays with arbitrary patterns in a 2D semiconductor crystal by transforming a single-layer crystal's patterned regions into another.

To do this, the researchers first produced molybdenum diselenide crystals in nanometer-thick layers then deposited silicon oxide protective patterns through standard techniques in lithography. The crystals' exposed regions were then bombarded with sulfur atoms generated from laser beams, replacing selenium atoms and forming molybdenum disulfide. When sharp junctions were formed on two semiconductor crystals, desired electronic building blocks have been made.

"We can literally make any kind of pattern that we want," said Masoud Mahjouri-Samani, a co-lead for the study, adding that patterns may also be concurrently made.

David Geohegan, who co-led the study with Mahjouri-Samani, said their work fulfilled the "building blocks" that would pave the way for the next generation of devices that would be sporting ultrathin forms, which would enable a number of applications.

The researchers reported their work in the journal Nature Communications. Aside from Mahjouri-Samani and Geohegan, authors for the study include Ming-Wei Lin, Mina Yoon, Kai Wang, Kai Xiao, Andrew Lupini, Ilia Ivanov, Jaekwang Lee, Alexander Puretzky, Leonardo Basile, Christopher Rouleau and Abdelaziz Boulesbaa.

The study was sponsored by the Office of Science at the U.S. Department of Energy. The National Secretariat of Higher Education, Science, Technology and Innovation of Ecuador also provided support through Basile.

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