New transistor’s superlative properties could have broad electronics applications

In 2021, a team led by MIT physicists announced the creation of a new, ultrathin ferroelectric material, or one in which positive and negative charges are separated into distinct layers. At the time, they noted the material’s potential for applications in computer memory and much more. Now, the same core team and colleagues—including two from a neighboring lab—have successfully built a transistor out of the material and shown that its properties are so useful that they could change the world of electronics.

Although the team’s results are based on a single transistor in the lab, “in many respects its properties already meet or exceed industry standards” for photovoltaic transistors produced today, says Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics, who led the work with physics professor Raymond Ashoury. Both are affiliated with the Materials Research Laboratory.

In my lab we primarily Basic Physics“This is one of the first, and perhaps most dramatic, examples of how basic science can contribute to something that can have a major impact on applications,” says Jarillo-Herrero.

“When I think about my entire career in physics, this is the work that I think could change the world 10 to 20 years from now,” Ashouri says.

Among the superior properties of the new transistor:

• It can switch between positive and negative. Negative charges– that is, the ones and zeros of digital information – at very high speeds, on a time scale of nanoseconds. (A nanosecond is one billionth of a second.)
• It’s extremely robust. After 100 billion swaps, it still works without any signs of degradation.
• The material behind this magic is just a billionth of a meter thick, one of the thinnest of its kind in the world. That could allow for denser computer memory storage. It could also lead to more energy-efficient transistors because of the effort required to switch the scales with the material’s thickness. (Ultra-thin transistors equate to extremely low voltages.)

Work is Published In the latest issue of SciencesThe co-lead authors of the paper are Kenji Yasuda, now an assistant professor at Cornell University, and Evan Zalis Geller, now at Atom Computing. Additional authors are Shirui Wang, a graduate student in physics at MIT; Danielle Bennett and Efthymios Kaxiras of Harvard University; Suraj S. Cheema, an assistant professor in the Department of Electrical Engineering and Computer Science at MIT and affiliated with the Electronics Research Laboratory; and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

What did they do

In ferroelectric materials, positive and negative charges spontaneously orient to opposite sides, or poles. When an external electric field is applied, these charges switch sides, reversing the polarization. Polarization switching can be used to encode digital information, and this information is nonvolatile, or stable over time. It will only change if an electric field is applied. For ferroelectric materials to have widespread application in electronics, all of this must happen at room temperature.

New photovoltaic material Reported in Sciences This system is based on atomically thin sheets of boron nitride stacked parallel to each other, a configuration not found in nature. In bulk boron nitride, the individual layers of boron nitride are rotated by 180 degrees.

It turns out that when an electric field is applied to this parallel stacked configuration, one layer of the new boron nitride material slides over the other, slightly shifting the positions of the boron and nitrogen atoms. For example, imagine that each of your hands consists of just one layer of cells. The new phenomenon is like pressing your hands together and then sliding one over the other slightly.

“So the miracle is that by moving the layers a few angstroms, you end up with radically different electrons,” says Ashouri. The diameter of an atom is about one angstrom.

Another miracle: “Nothing wears out during the slide,” Ashour continues. That’s why the new transistor can be swapped 100 billion times without deteriorating. Compare that to the memory in Data memory “This new material is made from traditional materials,” says Ashour. “Every time you write and erase a flash memory, it undergoes some degradation. Over time, it wears out, and that means you have to use some very sophisticated techniques to distribute where you read and write on the chip.” The new material could make those steps obsolete.

Collaborative effort

Yasuda, co-first author of the current book Sciences The paper commends the collaborations involved in the work. Among them, “We [Jarillo-Herrero’s team] Made by, and in collaboration with Ray [Ashoori] And [co-first author] Evan [Zalys-Geller]“We measured its properties in detail. That was very exciting,” says Ashour. “Many of the techniques in my lab were naturally applied to the work that was going on in the lab next door. It was a lot of fun.”

“There’s a lot of interesting physics behind this,” Ashori notes, that could be explored. For example, “if you think about the two layers sliding over each other, where does that sliding start?” Additionally, Yasuda says, could ferroelectricity be stimulated by something other than electricity, like a light pulse? And is there a fundamental limit to the number of switches the material can make?

But challenges remain. For example, the current method for producing the new photovoltaic materials is difficult and not conducive to mass manufacturing. “We made one transistor as a demonstration,” Yasuda says. “If people can grow these materials at wafer scale, we can make more and more of them.” He notes that various groups are already working toward this goal.

“There are some problems,” Ashouri concludes. “But if we can solve them, this material will fit into many potential future electronic devices. It’s very exciting.”

This story is republished with permission from MIT News (Website: www.mit.edu/newsoffice/), a popular site covering news about research, innovation, and teaching at MIT.