The influence of pulsed negative bias on the properties of silicon oxide barrier coatings prepared by microwave PECVD technology

Abstract In this paper, the plasma-enhanced chemical vapor deposition (PECVD) technique was used to prepare the barrier silicon oxide (SiO x ) films. The influence of applying a pulsed negative bias voltage on the deposition substrate on the film deposition and barrier properties was investigated. The plasma discharge characteristics were diagnosed by optical emission spectroscopy. The structure and morphology of the films were characterized by Fourier transform infrared absorption spectroscopy and atomic force microscopy. The barrier properties were characterized by testing the oxygen transmission rate (OTR). The results showed that the application of the pulsed negative bias voltage had a significant impact on the deposition rate, structure, surface morphology and barrier properties of the silicon oxide films. Meanwhile, with different duty cycle and voltage parameters, there were also differences in film deposition and properties. The application of the pulsed negative bias voltage led to a decrease in the film deposition rate, but the film barrier properties were significantly improved. Under certain process parameters, deposit a layer of silicon oxide film on the surface of polyethylene terephthalate (PET) film., the OTR of the prepared SiO x /PET composite films could be as low as 3.87 ml·m −2 ·d, which was much lower than 130 ml·m −2 ·d when not coated. After applying a pulsed negative bias voltage with a duty cycle of 20% and a voltage of −50 V on the deposition substrate, the OTR of the SiO x /PET composite films could be further reduced to 1.03 ml·m −2 ·d. This finding is of great significance for the research on the preparation of high-barrier PET composite packaging materials by PECVD technology.