A team of researchers from Tohoku University, National Institutes for Quantum Science and Technology (QST), and Cambridge University have demonstrated a new way to make a unique material called tin sulfide (SnS), which can help build better and more compact electronic devices. The novel method can successfully grow SnS in sheets so incredibly thin that they are comprised of just one layer of atoms. This safe and cost-effective strategy is expected to streamline the process of making SnS - which could mean the next tech upgrade is just around the corner.
"SnS is special because it can conduct electricity and respond to light in unique ways," explains Makoto Kohda (Tohoku University). "Our method makes it easier to study those unique properties, which are important because they could lead to faster, more efficient computers."
Spin-valleytronics is a cutting-edge area of research that takes advantage of both the "spin" and "valley" of tiny electron particles inside a computer with the aim of developing high-tech electronics with unprecedented efficiency. While SnS has many desirable traits, its Achilles heel is the fact that it is challenging to selectively form SnS from base tin (Sn) and sulfur (S). For example, it may sometimes produce SnS2 instead - like a waiter accidentally giving the customer the wrong dish. So, to make sure the material produced is exactly what the customer ordered, researchers developed an easier and safer process that can reliably produce entire sheets of SnS.
To achieve this feat, the researchers had a brilliantly simple solution: just heating sulfur and tin in the right way can grow pure, high-quality SnS crystals on ordinary silicon wafers. A computer-calculated phase diagram predicted that low sulfur levels should give SnS, while high sulfur levels should give SnS2. They tested that prediction in the lab by sliding the sulfur source closer or farther from the tin. Then, the researchers used operando scanning electron microscopy to watch the outer layers "sublime" away (going directly from a solid to a gas), leaving a monolayer film behind.
"Our findings could speed up how scientists discover and understand new physical effects using monolayer SnS," says Kohda.
Linking together three hot research areas (ferroelectrics, spintronics and valleytronics) opens the door to creating better electronics - especially those that use light and tiny spins to work faster and smarter.
The findings were published in Nano Letters on May 20, 2025.