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).

The polymer polyethylene terephthalate (PET) has been exposed to quantified beams of argon ions and oxygen atoms and molecules. The etch rate (ER) and the surface composition of PET thin films have been analyzed by real time in situ Fourier transform infrared spectroscopy (FTIR). After the onset of the exposure of PET to the ion beam, the ER decreases rapidly by one order of magnitude irrespective of the ion energy. This slowing down of the ER is caused by cross‐linking of the polymer surface. The steady state etch yields are generally orders of magnitude higher than predicted by computer calculations. The addition of oxygen to the particle flux is only changing the surface composition. At low ion energies, chemical sputtering dominates causing very high sputter yields. In addition, no threshold ion energy is observed. magnified image

Plasma modifications of polypropylene (PP) surfaces are analyzed by means of vacuum beam experiments. A plasma source provides Ar ion beams and a background of UV photons. Additionally, neutral oxygen beams are sent to perform reactive sputtering of PP. The etch rate and chemical state are monitored in real time by in situ Fourier transform infrared (FTIR) spectroscopy. At the onset of Ar bombardment, PP shows high sputter yields, which decrease down to a constant etch rate indicating the formation of a modified top layer. The stationary top layer is modeled as combination of a pristine fraction plus a cross‐linked fraction of amorphous hydrocarbon. Photon‐ and ion‐dominated etch processes provide different cross‐linking fractions, whereas the sputter efficiency is maximized at intermediate ion energies (200 eV).

Modification of the surface chemistry and correlated adhesive properties of polypropylene (PP) by means of an electron cyclotron resonance (ECR) oxygen plasma source is studied based on an in situ ultra-high-vacuum (UHV)-analytical approach. To determine the plasma induced chemical changes without exposure to atmosphere, X-ray excited valence band (VB) spectroscopy and core level X-ray photoelectron spectroscopy (XPS) are performed. Adhesive properties are characterized by means of UHV chemical force microscopy (UHV-CFM). Correlation of XPS and UHV-CFM data indicate that interactions between a SiO 2 -tip and the modified PP surface is dominated by hydrogen bonds between surface silanol groups on the tip and induced oxidized species on PP surface. Such interactions are maximized in the initial phase of surface oxidation.

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