| Gas barrier plastic containers are highly demanded to prolong the shelf life of products such as food, medicine and drink. Diamond like carbon (DLC) films are well known gas barrier materials with excellent optical transparency and chemical inertness. In this work, magnetized direct current (DC)/radio frequency (RF) hybrid plasma enhanced chemical vapor deposition (PECVD) has been proposed to fabricate DLC films on the inner wall of polyethylene terephthalate (PET) cylindrical foils. Behaviors of plasma generated by DC/RF hybrid voltage for coaxial cylindrical configuration have been studied by particle-in-cell (PIC)/Monte Carlo collision (MCC) computer simulation, furthermore, Langmuir probe has been utilized to measure the plasma generated in the PECVD chamber for DLC film deposition and a method based on magnetic field enhancement has been proposed to improve the plasma uniformity. The film deposition rate, structure and surface morphology has been characterized using scanning electron microscope, X-ray photoelectron spectra, Fourier transformed spectroscope and optical profiler, respectively. Meanwhile, film uniformity, adhesion, gas barrier property and stability has also been tested by UV-visible spectra, tensile test, gas permeability tester, contact angle tester and solution immersion method respectively. Ultimately, a multistage machine for DLC film deposition on inner wall of PET bottles has been designed and tested, which provides standards for industrial production.The plasma behavior results for coaxial cylindrical configuration simulated with PIC/MCC method demonstrated that the width and voltage of the sheath near the outer electrode could be adjusted by coupling with a DC bias, which is benefit for adjustment of ion energy. While the ion concentration could be enhanced significantly by enlarging the RF voltage amplitude, meanwhile, the sheath voltage is also improved. Furthermore, the plasma density could also be enhanced for higher gas pressure; however, the ion energy might be depressed.The RF/DC hybrid power source has been designed to control the RF voltage amplitude and DC bias independently. The Langmuir probe measurement results indicated that higher plasma density could be yielded when DC bias was -70V comparing to the discharge generated without DC bias or with positive DC bias. Otherwise, plasma density inside the chamber could also be enhanced for higher RF power and pressure. However, non-uniformity of plasma generated inside the chamber has been observed and could be modified by magnetic filed confinement effectively.Higher deposition rate of DLC film could be obtained at suitable higher RF power and acetylene pressure with high negative DC bias. The structure of DLC film governed by ion energy could be changed by controlling the DC bias, RF power and acetylene pressure. Higher sp~3 bonded carbon content might be achieved at higher negative DC bias and lower acetylene pressure. By covering a thin layer of DLC film, the smoother surface was observed.The film uniformity in axial direction characterized using optical transmittance value was improved significantly by magnetic field confinement. The adhesion strength of DLC film on PET measured using tensile tests was improved for films fabricated at higher negative DC bias and lower acetylene pressure when RF power is suitable. By depositing a thin layer of DLC film, the permeability of PET sample is significantly depressed. However, the gas barrier property might be weaken when the equivalent film thickness exceeds the critical value. The film stability results indicated that film with high water contact angle (>90°) showed better stability after immersion test in beer solution, which is related with sp~3/sp~2 ratio of DLC film.To research the feasibility of industrial application, multistation machine with 15 inner coating units has been designed and manufactured. DLC film scheduling deposition on the inner surface of PET bottles in different units has been achieved successfully.
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