Forward-looking: MIT scientists seeking breakthroughs in nuclear materials have made an unexpected discovery with major implications for microelectronics: they found they could use an X-ray beam not only to observe material failure in real time, but also to precisely control the amount of strain inside the material during experiments. This newfound ability could open new methods for enhancing the electrical and optical properties of semiconductor chips, giving engineers a practical tool for manufacturing advanced microelectronic devices.
The research, detailed in Scripta Materialia by senior author Ericmoore Jossou and colleagues, started as an effort to understand how critical reactor materials break down under intense radiation.
The team's setup involved firing extremely focused, high-intensity X-rays at nickel samples prepared through solid-state dewetting – a process that forms single crystals by heating thin films at high temperatures. Their goal was to recreate the harsh conditions typical of nuclear reactors and study corrosion and cracking as they occurred.
As the team refined their experiment, they noticed that by adjusting the duration and focus of the X-ray, they could manipulate the crystal structure by either relaxing or enhancing internal strain. The effect was most pronounced when a layer of silicon dioxide was used as a buffer between the nickel and its silicon substrate.
This advance goes beyond academic curiosity, offering a scalable technique for the semiconductor industry.
Strain engineering, which means to deliberately distort the crystal lattice of materials to improve performance, is an essential part of building faster, more efficient chips. Traditionally, this involves mechanical methods or the introduction of specific layers during fabrication.
The MIT discovery suggests that X-ray beams could become a precision tool for tuning strain while a chip is being manufactured, representing a two-for-one gain for materials science: deeper knowledge about failure in nuclear environments and a new technology for electronics manufacturing.
These unexpected results emerged as the researchers attempted to stably image nickel crystals under stress. Preparing usable samples required overcoming chemical reactions that could derail experiments, such as the formation of unwanted compounds between nickel and silicon.
The introduction of a thin silicon dioxide buffer not only stabilized the crystals but also allowed the team to relax strain enough for phase retrieval algorithms to reconstruct the 3D shape of the samples in real time.
This capability of watching crystals fail in three dimensions as they are exposed to simulated reactor conditions, provides crucial data for designing tougher materials for reactors, naval propulsion systems, and other demanding environments.
The work was carried out by a team including Ericmoore Jossou, David Simonne, Riley Hultquist, Jiangtao Zhao, and Andrea Resta, and was funded by the MIT Faculty Startup Fund and the US Department of Energy. The researchers now plan to expand their studies to more complex alloys and to fine-tune how buffer thickness influences strain control.