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

Abstract

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 SnS2(1-x)Se2(x) (0 ≤ x ≤ 1) ternary alloys grown via chemical vapor transport (CVT) with tunable compositions. Polarized micro-Raman spectroscopy shows the existence of intralayer Eg and A1g modes in all the compositions. The A1g mode demonstrates a pronounced resonant intensity, whilst the Eg mode is significantly weaker. In the ternary compositions, two groups of Eg and A1g 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 SnSe2) to 2.3 eV (for pure SnS2), indicating high-quality alloy nanosheets of SnS2(1-x)Se2(x). The optical and electrical applications, such as photodegradation, photoconductivity, and thermoelectric performance are also explored. The alteration in selenium composition within SnS2(1-x)Se2(x) 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.