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Ultra-clean production platform produces almost ideal 2-D transistors

Ultra-clean production platform produces almost ideal 2D transistors

An improved optical microscope image of a Hall-bar structure used to characterize transistor properties for devices made with ultraclean-transferred contacts. The long radial lines, made of deposited gold, connect the small contacts in the center of the device with large probe pads for easy measurements. Credit: Min Sup Choi / Columbia Engineering

Semiconductors, the basic building blocks of transistors, microprocessors, lasers and LED & # 39; s, have made progress in IT, memory, communication and lighting technologies since the mid-20th century. Recently discovered two-dimensional materials, which have many superlative properties, have the potential to promote these technologies, but creating 2-D devices with both good electrical contacts and stable performance has proved a challenge.

Researchers at Columbia Engineering report that they have shown an almost ideal transistor made from a two-dimensional (2-D) material stack – with only a two-atom thick semiconductor layer – by developing a completely clean and damage-free manufacturing process. Their method exhibits greatly improved performance compared to 2-D semiconductors manufactured with a conventional process, and could provide a scalable platform for making ultra-clean devices in the future. The study was published today in Natural electronics.

"Making devices from 2D material is a messy undertaking," says James Teherani, assistant professor of electrical engineering. "Devices vary enormously from run to running and often degrade so quickly that you see performance decrease while you still measure them."

Tired of inconsistent results, the Teherani team wanted to develop a better way to make stable devices. "So," he explains, "we decided to separate the original device from the dirty manufacturing processes that lead to variability."

Video about the differences between 2D and 3D materials

As seen in this new study, Teherani and his colleague & # 39; s developed a two-step, ultra-pure, nanofabrication process that the & # 39; messy & # 39; separates manufacturing steps, those where & # 39; dirty & # 39; metallization, chemicals and polymers are used to form electrical connections to the device – of the active semiconductor layer. Once they have completed messy manufacturing, they can pick up the contacts and transfer them to the clean active device layer, preserving the integrity of both layers.

"The thinness of these semiconductors is a blessing and a curse," says Tehran. "Although the thinness allows them to be transparent and to be picked up and placed wherever you want, the thinness also means that there is almost no volume anymore – the device is almost full surface. This means that any surface dirt or pollution will really degrade device "

Video about the step-by-step nanofabrication of 2D material stacks

Today, most devices are not encapsulated with a layer that protects the surface and contacts from contamination during manufacture. The Teherani team demonstrated that their method can now not only protect the semiconductor layer, so that they do not see performance deteriorate over time, but it can also produce high-quality devices.

Tehran collaborated with Jim Hone, Wang Fong-Jen, Professor of Mechanical Engineering, who used the manufacturing and analysis facilities of the Columbia Nano Initiative and the Materials Research Science and Engineering Center in Columbia, funded by the National Science Foundation. The team made the transferred metal contacts embedded in insulating hexagonal boron nitride (h-BN) outside a glove box and then transferred the contact layer dry to the 2-D semiconductor, which was originally stored in a nitrogen glove box. This process prevents direct metallization-induced damage while at the same time providing encapsulation to protect the device.

  • Ultra-clean production platform produces almost ideal 2D transistors

    The manufacturing process for transferred contacts that provide almost ideal transistors. Transferred contacts prevent contamination and damage to the 2D semiconductor that occurs during the fabrication of conventional contacts. Credit: Min Sup Choi / Columbia Engineering

  • Ultra-clean production platform produces almost ideal 2D transistors

    A Hall-bar device structure (see inset) is tied to a 16-pin chip carrier. The chip carrier enables extensive electrical characterization of the device at both low temperatures and high magnetic fields. Credit: Min Sup Choi / Columbia Engineering

Now that the researchers have developed a stable, repeatable process, they use the platform to bring equipment that can move out of the laboratory into real technical problems.

"The development of high-quality 2D devices requires progress in the semiconductor materials from which they are made," Teherani adds. "More accurate tools such as ours will allow us to build more complex structures with potentially greater functionality and better performance."

The study bears the title "Transferred via contacts as a platform for ideal two-dimensional transistors."

Photo baptism in 2-D materials for the manufacture of logical devices

More information:
Transmitted via contacts as a platform for ideal two-dimensional transistors, Natural electronics (2019). DOI: 10.1038 / s41928-019-0245-y, http://dx.doi.org/10.1038/s41928-019-0245-y

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Columbia University School of Engineering and Applied Science

Ultra-clean production platform produces almost ideal 2-D transistors (2019, 17 May)
recovered May 17, 2019
from https://phys.org/news/2019-05-ultra-clean-fabrication-platform-ideal-d.html

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