Researchers from Tohoku University, the National Institutes for Quantum Science and Technology (QST), and Cambridge University have managed to create a monolayer tin sulfide (SnS) material, which could be suitable for spin-valleytronics applications.
The researchers explain that SnS is special because it can conduct electricity and respond to light in unique ways. But io far it has been challenging to selectively form SnS from base tin (Sn) and sulfur (S) - sometimes other materials are produced instead, such as SnS2 instead. Now the 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.
Now the researchers can use the new films and study their use in spin-valleytronic applications.