On 9 September 2021, the research on thickness-dependent Raman active modes of SnS thin films led by Prof. Katsunori Wakabayashi (School of Engineering) were published in AIP Advances and selected as Featured Article (as a one of the journal's best articles). In addition, the paper was also selected as one of the Scilight (science highlight) articles published by the American Institute of Physics (AIP), which features only the most outstanding research results. The first author of this paper is Mr. Itsuki Yonemori (Department of Advanced Energy Nanoengineering, completed in March 2021), and it is the result of collaborative research between IISER Tirupati, India, and the Graduate School of Engineering, University of Tokyo.

In recent years, research on atomically thin and two-dimensional materials is a one of the most active fields in condensed matter physics, nanoscience, and nanotechnology. In this paper, we focused on tin sulfide (SnS), which has strong thickness-dependent ferroelectricity, and clarified its electronic and phonon states by using first-principles calculations based on density functional theory. In particular, we have clarified the layer number dependence of the Raman active mode and the layer number dependence of the surface phonon mode peculiar to SnS. These results are expected to be useful for the analysis of the layer number and stacking structure of the synthesized SnS in the future.