Structural, optical and electrical properties in multilayer SnS2(1-x)Se2(x) compounds for energy, thermoelectric and photocatalytic application

Band gap engineering is crucial in the development of two-dimensional layered materials in nanoelectronics, optoelectronics, and photonics fields. In this study, we present characteristics of layered SnSSe (0 ≤ x ≤ 1) ternary alloys grown via chemical vapor transport (CVT) with tunable compositions. Polarized micro-Raman spectroscopy shows the existence of intralayer E and A modes in all the compositions. The A mode demonstrates a pronounced resonant intensity, whilst the E mode is significantly weaker. In the ternary compositions, two groups of E and A modes undergo shift, reflecting lattice and bond transitions from S-rich to Se-rich compositions. Micro-thermoreflectance and optical transmission spectroscopy reveal tunable optical properties consistent with the alloy-composition change. All samples exhibit a single band-edge transition peak, shifting from 1.3 eV (for pure SnSe) to 2.3 eV (for pure SnS), indicating high-quality alloy nanosheets of SnSSe. The optical and electrical applications, such as photodegradation, photoconductivity, and thermoelectric performance are also explored. The alteration in selenium composition within SnSSe is observed to significantly influence potential applications of the materials. The materials with a predominant selenium composition exhibit superior electrical and thermoelectric properties, whereas those with a sulfur-dominant composition manifest enhanced optical characteristics. The engineered 2D structures presents promising opportunities for investigating their fundamental physical properties and also exploring their wide-range applications in electronic and optoelectronic devices, as well as in the field of energy and photocatalytic application.