Thermodynamically Driven Phase Transition and Thermal Properties of Composite SnSex Nanoparticles on Flexible Substrate
Ling Lee1*, Arumugam Manikandan1, Chia-Wei Chen1, Yu-Lun Chueh1
1Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:Ling Lee,
Beyond typical transition metal diachalcogenides, tin-based chalcogenides are currently considered as promising two-dimensional layered materials for energy harvesting. In particular, tin monoselenide (SnSe), a p-type orthorhombic semiconductor with a bandgap of 0.86 eV, exhibits surprising outstanding thermoelectric properties owing to the unexpectedly low thermal conductivity and the high power factor. Moreover, since tin diselenide (SnSe2) is an n-type hexagonal semiconductor with a bandgap of 1.0 eV, the pn junction in between is expected for photovoltaics. However, these purposes are still challenged by the accurate control of phases in the SnSex system during growth. In this work, we demonstrated the phase transition between SnSe and SnSe2 by using plasma-assisted post selenization process, and established a thermodynamically driven mechanism. We successfully grown a thin film with thickness less than 10 nm, which consists of composite SnSex nanoparticles on flexible muscovite substrate. Tin monoselenide and diselenide dominates at the selenization temperature of lower than 175 °C and higher than 250 °C, respectively. In addition, thermal properties, including the non-linear temperature-dependent Raman shift and the thermal conductivity of SnSex thin film, are also investigated by utilizing the Raman spectroscopy. These stoichiometric, crystallographic, and thermal properties would provide effective information of flexible energy harvesting devices based on tin chalcogenide materials.

Keywords: SnSe, SnSe2, phase transition, muscovite, Raman