Effects of RF-Bias Power Application in an Inductively Coupled CF4 Plasma on the Nanoscale Morphology and Chemical Bond Structure of Polyethylene Terephthalate Surface

By varying the radio frequency-bias power in an inductively coupled CF
₄
plasma, we have modified the nanoscale morphology and chemical bond structure of polyethylene terephthalate (PET) surface. Specifically, the ion impingement increased the surface roughness and created CFn (n= 2, 3) functional groups on the PET surface, making it hydrophobic. Also observed was a significant increase in the hydrophobicity of the plasma-modified surfaces over the course of several days following the treatment (a hydrophobic recovery). X-ray photoelectron spectroscopy analysis revealed that this spontaneous transformation to a more hydrophobic surface is accompanied by a decrease in the fluoride ion content. The change of plasma density and electron temperature with increasing bias power were discussed. In addition, the change of the ion energy distribution with increasing bias power was investigated.