Assessment of the effect of surface functionalization of oxygen and argon microwave plasma on PVA films for optoelectronic devices

Abstract This study explores the enhancement of optical properties in polyvinyl alcohol (PVA) polymer using a low-pressure microwave plasma reactor, adapted from a microwave oven. The research focuses on the effects of oxygen and argon plasma treatments at a consistent power of 1000 W, a flow rate of 6 L min −1 , and a pressure of 16 mbar on PVA films. The optimal treatment times of 10 s and 15 s were identified as particularly effective in improving the optical characteristics of the PVA films, which were created using a solution casting method. The optical properties were analyzed using a UV-vis spectrophotometer across a wavelength range of 200–900 nm. The absorption spectrum revealed a significant absorption peak at around 210 nm (photon energy = 5.8 eV) for all plasma-treated PVA films, with a subsequent decrease in absorbance. Notably, the transmittance for the PVA-oxygen treated film at 10 s reached a maximum of 90.36% beyond 360 nm, attributed to increased hydrophilicity from the oxygen content. Similar trends were observed in the extinction coefficient (k) and optical conductivity ( σ opt ). The optical energy band gap, calculated using the Tauc relation for both direct and indirect allowed transitions, decreased from 5.32 eV and 4.80 eV to 4.82 eV and 4.35 eV with longer exposure times. The study also noted that skin depth diminishes as the incident energy photon value increases, indicating that penetration becomes more challenging at higher frequencies. The PVA-oxygen plasma treated film, after a 10 s exposure, has improved optical properties, making it suitable for various electronic industries.