Effect of plasma processing on the morphological and electrical properties of polyethylene terephthalate (PET) substrate

Atmospheric pressure plasma (APP) operates at atmospheric pressure eliminating the requirement for a vacuum system and making it more viable for large area applications. Furthermore, generally it has low ion energies, a high density of electrons and reactive radicals compared to the low-pressure plasmas. These characteristics make it safe, versatile, and effective technology, suitable for applications in flexible electronics and biomedical surface treatments. In this article, we performed a comparative study of surface properties of polyethene terephthalate (PET) film modified by two low-temperature plasma processes, namely an atmospheric pressure plasma discharge (APP) treatment and low-pressure plasma (LPP) treatment. The surface activation and structural properties of plasma treated film surfaces were studied using contact angle measurement, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results show that both processes modified the surface of PET film and increased the hydrophilicity. However, micrographs from SEM and AFM revealed a defect-free and smoother surface morphology for APP-treated PET film. To explore the electrical properties, flexible diodes (PET/Al/ZnO/Ag) were fabricated on both types plasma treated of PET substrates and critical results such as rectification ratio and leakage current were analyzed using current ( I ) –voltage ( V ) characteristics at room temperature. Devices made on APP-treated PET substrate have shown an improved rectification ratio (∼ one order) with reduced leakage current compared to the devices made on LPP- treated PET. It is inferred that the low roughness, uniform surface modification, and excellent wettability of APP-treated PET led to formation of low defect films in the diode • Atmospheric vs low-pressure plasma treated PET substrates • Improved surface roughness and wettability of atmospheric plasma treated PET substrate • Impact of plasma treatment on devices made on flexible substrates – case study of a diode