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Solving the puzzle of 2D disorder

Solving the puzzle of 2D disorder

Device structure and hysteretic behavior of the gate voltage swing. Credit: Northwestern University

When players try to solve word games, they try to put together clues to find the solution. Sure it helps to have a strong vocabulary, but finding the right answers to those puzzles has as much to do with logic and strategy as it is with being a word artist.

Using a surprisingly similar process, an interdisciplinary team of Northwestern Engineering researchers has put together a method to determine how different 2D materials respond to disorder — by testing some materials that could potentially replace silicon in new transistors and sensors.

“The analysis method will lead to a better understanding of disorder potential in 2D materials to help make faster transistors, as well as better gas sensors that can more easily distinguish different gases,” said Matthew Grayson, a professor of electrical and computer engineering at the McCormick School of Engineering, and a researcher. from the authors of the study.

in the paper “Field-effect Conductivity Scaling for Two-dimensional Materials with Tunable Impurity Density,” published June 16 in the journal 2D materialsthe researchers developed a method to determine the fingerprint of the neighboring condition as seen through a 2D material.

Vinayak Dravid, Abraham Harris Professor of Materials Science and Engineering, and Mark Hersam, Walter P. Murphy Professor of Materials Science and Engineering, also contributed to the effort. Chulin Wang, a Ph.D. candidate in Grayson’s research group, was the lead author of the paper.

In science, disorder refers to imperfections or nearby charges that could scatter an electron’s otherwise straight path. 2D materials such as graphene are particularly prone to nearby disorder as they are literally a few atoms thick at most

“The characterization of the disorder is paramount for understanding and improving the performance of 2D materials,” Grayson said. “This paper shows that there is a universal curve that serves as a fingerprint of that disorder. While different doses of disorder seem to result in completely different behaviors, these behaviors all represent individual threads of an overall carpet.”

Here comes the similarity between science and games you play on your phone or printed newspaper.

Using 2D material samples developed by the Hersam and Dravid groups, Grayson and his team implemented a new method to measure electrical conductivity curves using a cryostat, a device that stores samples at low temperatures for microscopic examination. At room temperature, the charges that form disorder can shift freely until they reach equilibrium, but when frozen in the cryostat, the disorder is frozen in place.

Each individual conductivity curve resembles a puzzle piece. The researchers then used an empirical rule to put all the curves together until they formed a complete picture.

Sounds familiar?

They then used physical arguments to understand why this rule works so well. As a result, they solved the riddle of how each of the materials studied reacts to a specific class of imperfections.

“The impressive continuity of this picture when all the puzzle pieces were in place inspired us to dig deeper into physics to understand what the underlying reason for this behavior must be,” Grayson said. “The same mindset that the general public uses to solve their daily Wordle or crossword puzzle is applied here.”

These findings also have implications for future 2D materials research.

“Instead of seeing individual devices made of the same 2D material as a bunch of puzzle pieces that each need to be studied individually, you can now locate where a particular monster fits in the previously solved puzzle,” Grayson said, “so that each individual piece becomes a piece.” immediately recognized as part of a greater whole.

Method analyzes non-uniform conductors with a magnetic field

More information:
Chulin Wang et al, Field effect conductivity scale for two-dimensional materials with adjustable impurity density, 2D materials (2022). DOI: 10.1088/2053-1583/ac72b0

Provided by Northwestern University

Quote: Solving the Puzzle of 2D Disorder (2022, June 16) retrieved June 16, 2022 from https://phys.org/news/2022-06-puzzle-2d-disorder.html

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