System Bits: Jan. 22

Toward more trusted microelectronics
David Crandall, an associate professor in Indiana University Bloomington’s School of Informatics, Computing and Engineering, is collaborating with other researchers through the Indiana Innovation Institute (IN3) to work on technology challenges for private industry and the U.S. Department of Defense.

Crandall is currently tackling trusted microelectronics, a prime concern for the military/aerospace sector. “Our role in this project is to use computer vision and machine learning techniques to help ensure the integrity of the supply chain around microelectronics. One way is to use computer vision to inspect integrated circuits to see whether there is something suspicious that might suggest they are damaged or counterfeit,” he says in this interview. “The challenge of the computer vision work we’re doing with IN3 — and with a lot of real-world problems — is that it requires very fine-grain analysis. We’re not trying to distinguish cats from dogs or cars from pedestrians; we’re trying to find very subtle differences in integrated circuits that might signal a problem. That’s really the challenge: to bring techniques that have been successful in the last few years in consumer photography to this new field that has unique challenges.”

He adds, “The problem is really important. Modern society depends on the safe, secure, reliable operation of digital devices. If they can’t be trusted, that rips apart a lot of what our society is based on. We — researchers in the state of Indiana — are in a unique position to attack this problem because of Purdue’s expertise in microelectronics; Naval Surface Warfare Center Crane’s capabilities; and IU’s expertise with chemistry, machine learning and engineering. We’re in the right place at the right time to have a real impact on this problem.

“There are many possible approaches. One is to use computer vision to inspect the surface of a package of an integrated circuit, checking the part number and looking for suspicious visual features that might indicate it has been modified. Another approach uses Sara Skrabalak’s work in adding unclonable fingerprints to integrated circuit packages and using computer vision techniques to verify that they are authentic. We can also inspect the internal circuitry of the integrated circuit using various imaging techniques,” Crandall concludes.

The unusual chemistry of MXenes
Missouri University of Science and Technology researchers report their discovery that 2D titanium carbide materials, known as MXenes, can react to water without the presence of other oxidizers. This discovery may lead to new insights into the unusual chemistry of MXene materials and may have an impact on storage and device manufacturing with MXenes, sometimes called conductive clays.

“Our new findings are important because now we know it is water itself rather than oxygen that MXenes need to be protected from during manufacturing and storage,” says Shuohan Huang, a doctoral student in chemistry at Missouri S&T. Dr. Vadym Mochalin, associate professor of chemistry at Missouri S&T and the principal investigator of this project, says researchers are excited about the potential use of MXenes in energy storage and harvesting applications, such as batteries, supercapacitors, and triboelectric nanogenerators, which convert wasted frictional energy into electricity.

“The reactivity of MXenes toward water we’ve demonstrated not only changes the common perception about resistance of titanium carbide to hydrolysis in ambient conditions, but also points out the striking differences in chemical properties between bulk and 2-D forms of the same material,” says Mochalin. “It seems that in their 2-D state, transition-metal carbides are quite reactive. With our result, we’re looking forward to follow-up studies of their rich chemistry in reactions with water and other molecules, including organic compounds, as well as studies into MXenes’ possible catalytic properties.”

Tuning iron-based superconductors
High-temperature superconductors, the subject of the 1987 Nobel Prize in Physics, have had a relatively low profile in research and development for the last few decades. Rice University researchers are working with iron-based superconductors and how they could be potentially utilized as quantum materials.

“Our work demonstrates a new design principle for tuning quantum materials to achieve unconventional superconductivity at higher temperatures,” said Rice’s Qimiao Si, the lead theoretical physicist on the studies, which investigate unusual patterns of superconductivity that have previously been reported in iron selenide. “We show how nematicity, an unusual electronic order, can boost the chances that superconductivity will arise from electron-pairing in specific orbitals,” said Si, director of the Rice Center for Quantum Materials (RCQM) and the Harry C. and Olga K. Wiess Professor of Physics and Astronomy. “Tuning materials to enhance this effect could foster superconductivity at higher temperatures.”

In nematic systems, there is a higher degree of order in one direction than another. In a box of uncooked spaghetti, for example, the noodles are aligned longwise but disordered if viewed in the perpendicular direction.

“In the present work, we showed that a nematic order drastically enhances orbital selectivity in the normal state at temperatures above the superconducting transition temperature,” said Rong Yu of China’s Renmin University, lead author of the Physical Review Letters paper on this research.

“Our results provide a natural understanding of very striking results that were recently reported based on painstaking measurements of the superconducting gap in iron selenide with scanning tunneling microscopy,” said Haoyu Hu, a graduate student at Rice, and the lead author of the Physical Review B paper.