Investigations on Plasma Interactions with Soft Materials for Fabrication of Flexible Devices

Abstract

  Interactions of ions, radicals and photons in VUV-UV regions from Ar plasmas and Ar-O₂ mixture plasmas with polymer surfaces were investigated on the basis of surface morphological changes and depth analyses of chemical bonding states in the nano-surface layer of polyethylene terephthalate (PET) films. The depth analyses of chemical bonding states were carried out with hard x-ray photoelectron spectroscopy (HXPES) and conventional x-ray photoelectron spectroscopy (XPS). The AFM images indicated that oxygen ions and/or radicals have a significant effect on the surface morphology. The HXPES results indicated that the degradation of the chemical bonding states due to the plasma exposure was insignificant in deeper regions up to about 50 nm from the surface. Whereas, the conventional XPS analysis showed that C-O bond and O=C-O bond decreased after exposure to the Ar plasmas which have high energy ion (over 7 eV). Furthermore, the C-O bond and the O=C-O bond increased after exposure to the Ar-O₂ mixture plasma and VUV-UV photons from the plasma. These results suggest that it is possible to prevent the decomposition of functional groups via controlling the plasma to suppress the ion energy less than 6eV. Moreover, it is important to control reactive species and VUV-UV photons for development low-temperature and low-damage plasma processes.