Deposition of diamond-like carbon films on interior surface of long and slender quartz glass tube by enhanced glow discharge plasma immersion ion implantation

•DLC films are successfully deposited on tube inner surface with 0.9 mm diameter.•The DLC films' deposition rate is as high as 1.3 μm/min.•Electron mean free path & collision frequency are used to explain deposition.

Diamond-like carbon (DLC) films are deposited on the interior surface of 100 mm long quartz glass tubes with inner diameters of 6, 4, and 0.9 mm by enhanced glow discharge plasma immersion ion implantation (EGD-PIII) at 10 kV. The acetylene plasma is generated inside the tube by electrons created in the plasma near the substrate and secondary electrons from ion bombardment. Acetylene gas pressure distribution obtained from finite element method shows that the pressure varies linearly from the inlet to the outlet of the tube. The electron mean free path, λe, and collision frequency, νe, are introduced to qualitatively explain the non-uniform DLC film thickness. Raman scattering indicates that the DLC films at different locations have a similar structure.