Temperature-dependent Raman spectroscopy in double spiral WS2 nanostructures

Abstract

The exploration of complex morphological hierarchies in two-dimensional transition metal dichalcogenides (TMDs), such as spiral structures, is critical for advancing their applications in phonon engineering and nano thermites. However, the intricate thermal properties of multi-spiral architectures, which are expected to exhibit more complex strain fields and interlayer interactions, remain largely unexplored. Addressing this gap, this study presents a temperature-dependent Raman spectroscopy investigation on a double-spiral WS₂ structure over the range of 150–450 K. Using multi-peak Lorentzian fitting, the first-order optical modes E¹_2g and A_1g were successfully extracted. The results show that, relative to the monolayer and single-spiral structures, the double-spiral WS₂ has a weaker temperature response. Layers within the same spiral domain show similar temperature dependent Raman shift behaviors, whereas those from different spirals display distinct trends. Fitting with thermal expansion and multiphonon models reveals that the nonlinear temperature dependence is primarily governed by thermal expansion, which can be directly described by the thermal expansion coefficient. And the three-phonon process dominating the shift magnitude—except in the edge layer. Furthermore, the analysis suggests potential evidence consistent with the theoretically predicted negative thermal expansion effect in WS₂, which merits further investigation.