Investigation of working pressure on the surface roughness controlling technology of glow discharge polymer films based on the diagnosed plasma

The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer (GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon (C₄H₈/H₂) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer (MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy (FT–IR), field emission scanning electron microscope (SEM) and white-light interferometer (WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C₄H₈/H₂ plasma reduces with an increase in the working pressure. At a low working pressure, the C–H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH₃/CH₂ ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa, the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 μm h⁻¹, and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.