May 17, 2019 01:46 PM EDT
According to the report of researchers at Columbia Engineering, they have demonstrated a nearly ideal transistor made from a two-dimensional (2D) material stack - with only a two-atom-thick semiconducting layer - by developing an immaculate and damage-free fabrication process.
The method of the researchers reveals vastly improved performance compared to 2D semiconductors fabricated with a conventional process and could offer a scalable platform for creating ultra-clean devices in the future. The team published their study in Nature Electronic.
An associate professor of electrical engineering, James Teherani, said that making devices out of 2D materials is a messy business. Devices vary wildly from run to run and often degrade so fast that you see performance diminish while you still measure them.
When Teherani grew tired of the inconsistent results, he and the team set out to develop a better way to make stable devices. He explained further that they decided to separate the pristine device from the dirty fabrication processes that lead to variability.
The researchers also showed in the study how they developed a two-step, ultra-clean nanofabrication process that separates the "messy" steps of fabrication - those that involve "dirty" metalization, chemicals, and polymers used to form electrical connections to the device, from the active semiconductors layer. After completion of the messy fabrication, the team could pick up the contacts and transfer them onto the clean, active device layer, preserving the integrity of both layers.
Teherani perceived the thinness of these semiconductors as a blessing and a curse. Though the thinness allows them to be transparent and to be picked up and placed wherever you want them, the thinness also means there's nearly zero volume, and the device is almost entirely surface. Due to this, any surface dirt or contamination will indeed degrade a device.
At present, a layer encapsulates most devices, and it protects the surface and contacts from contamination during fabrication. Teherani's team revealed that their method can now not only protect the semiconductor layer so that they don't see performance degradation over time, but it can also yield high-performance devices.
Since the team has developed a stable, repeatable process, they are using the platform to make devices that can move out of the lab into real-world engineering problems.
While explaining, Teherani added that the development of high-performance 2D devices requires advances in the semiconductor materials from which they are made. More precise tools like theirs will enable them to build more complex structures with potentially greater functionality and better performance.
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