Surface Modification of Polypropylene (PP) by Argon Ions and UV Photons

Abstract

The surface modification of polypropylene (PP) by monoenergetic argon ions and UV photons is evaluated in a particle beam experiment. Thereby, the polymer pre-treatment in a plasma process can be mimicked. The etching and chemical modification of the spin-coated PP thin films is monitored in real-time by in situ Fourier transform infrared spectroscopy (FTIR). It is shown that the initial exposure to the plasma ion source causes a modification of the film surface, which slows down the initially high etch rate. The separately measured UV-induced damage is more severe compared to the oxygencontaining polymer polyethylene terephthalate (PET).

Modeling of Charging on Unconventional Surface Morphologies of PMMA Substrates During Ar Plasma Etching

“…By using different v and e þ , the etching yield by TRIM, EY TRIM (e þ , v), was calculated. However, the etching yield calculated by TRIM was found orders of magnitude lower compared to the experimental measurements of Yoshimura et al This large difference is expected especially for low energy ions: [52,53] The polymeric surface consists of weakly interconnected long polymeric chains, whereas TRIM models an amorphous solid assuming a strongly interconnected carbon network. As a consequence, a single bond breaking event within a collision cascade may release large polymer fragments in case of a real polymeric surface, whereas the removal of only single Carbon atoms is most likely during the sputtering of a strongly interconnected carbon network.…”

Validation of etching model of polypropylene layers exposed to argon plasmas

“…The thickness variations because of etching under different supplied powers and different substrate bias voltages have been measured by single‐wavelength ellipsometry. Subsequently, the parameters of the modified surface model obtained from beam experiments with PP have been fitted to the experimental data . This validation has the following technical and scientific implications: (a) It confirms that the etching model encompasses the most relevant physical aspects governing plasma–material interactions; and (b) the results are promising for the application of the etching model to further plasma experiments.…”

Review Article: Unraveling synergistic effects in plasma-surface processes by means of beam experiments

“…The source of internal reactive species is reduced since no oxygen is present. On the other hand, the structure of PP is more sensitive to UV photons than in the case of PET, which leads to a synergistic effect between argon ions and UV radiation: the sputter yield by Ar + ions is maximized at 200 eV 4 . This combined action of ions and photons toward a very efficient etching is consistent with the measured IR spectra of the modified top layer, which fits perfectly with untreated PP and indicates that net etching without chemical conversion takes place at this ion energy 39 …”

“…Therefore, the understanding of the effects of ions, radicals, reactive neutrals, and UV photons at a metal target surface is crucial for the development of reactive sputtering models 4 . A prominent example is the ion-enhanced oxidation and the ion-induced secondary electron emission (SEE) from metal and metal oxide targets that can be described by an extension of Berg's magnetron sputter hysteresis model 5,6 …”