Semiconducting Ferroelectric SnS<sub>1-<i>x</i></sub>Se<i><sub><i>x</i></sub></i> van der Waals Alloy Flakes.

Sutter, Eli; Ghimire, Pramod; Sutter, Peter · Nano Lett · 2025

basic_science · Level V

Where this comes from

Abstract

Single-layer monochalcogenides are predicted to be in-plane ferroelectrics but are challenging to obtain in the 2D limit. Recent work showed that synthetic few-layer SnSe and SnS flakes also support ferroelectricity. Key properties such as the Curie temperature may become tunable via anion substitution in SnS<sub>1-<i>x</i></sub>Se<sub><i>x</i></sub> alloys. Hence, protocols need to be developed that produce ferroelectric few-layer alloy crystals. Here, we report SnS<sub>1-<i>x</i></sub>Se<sub><i>x</i></sub> alloy flakes across the entire composition range obtained by a highly reproducible growth process using mixed SnS/SnSe precursors. Characterization by electron microscopy and diffraction, X-ray dispersive spectroscopy, and Raman spectroscopy shows the flakes to be high-quality single crystals whose phonon modes and optical bandgaps interpolate between SnSe and SnS. Thin SnS<sub>1-<i>x</i></sub>Se<sub><i>x</i></sub> flakes across all compositions carry ubiquitous stripe domain patterns, i.e., the flakes are ferroelectric with twin domain walls. Such composition-tunable alloy flakes can support research on the fundamental mechanisms of in-plane ferroelectricity in few-layer monochalcogenide van der Waals semiconductors.