Room-temperature deposition of flexible SnS thin films via sulfur-plasma-based reactive sputtering

Fabrication of crystalline sulfide thin films on polymer substrates is typically constrained by the low heat resistance of the polymers and the thermal expansion mismatch between the films and the substrates. In this study, crystalline tin(II) sulfide (SnS) thin films were deposited on polyethylene terephthalate (PET) substrates at room temperature by sulfur-plasma-based reactive sputtering using a metallic Sn target and a sulfur-plasma source. The resulting SnS thin films on the PET substrates possessed a crystal phase exhibiting a preferential orientation, and adhesion properties comparable to those of thin films deposited on SiO2 glass. Bending tests indicated that the electrical resistance of the films remained stable down to a bending radius of 12 mm and showed robust durability under cyclic bending at a radius of 15.2 mm. These results confirm that the SnS thin films possess sufficient flexibility for practical applications, such as wearable devices and curved solar cells. The findings indicate that sulfur-plasma-based reactive sputtering provides a versatile and effective route for the direct integration of various sulfide semiconductors onto flexible substrates, accelerating the development of sulfide-based flexible electronics.