L.S Farenzena

Modifications in the chemical bonding and optical absorption of PPS by ion bombardment

Abstract Commercial-grade thin poly(p-phenylene sulphide) (PPS) foils, 2 μm thick, have been bombarded with 1H+ (380 keV), and with 0.61 MeV/amu 4He+, 12C2+, 16O3+, 32S3+, 79Br9+ and 127I14+ ions. The completely modified foils have been analyzed by Fourier transform infrared absorption spectroscopy (FTIR) and by ultraviolet-visible absorption spectroscopy (UV-VIS). The bond breaking and rearrangement processes were followed by using the FTIR results. The absorbance of bands related to CS, SS, CH and most of the ring carbon bonds show an exponential decrease as a function of fluence. The absorption bands most sensitive to the ion bombardment are those assigned to CS and SS bonds. The CC and CH bonds are less sensitive and certain absorption band changes indicate carbon-carbon aliphatic and or aromatic conjugation, due to their increasing intensity as a function of the ion fluence. Damage cross sections have been extracted from the plots of IR absorbance versus fluence. The values of the damage cross sections obtained scale roughly with the square of d E d x (independent of the nature of the chemical bond). The optical absorption coefficient has also been followed as a function of the ion fluence.

Probing glass transition of PMMA thin films at the nanometer scale with single ion bombardment and scanning force microscopy

Abstract Poly(methyl methacrylate) (PMMA) thin films maintained at temperatures from −196 up to 150 °C are bombarded at grazing angles by 20 MeV Au ions at very low fluences. Immediately after the irradiation, the samples are cooled down at two distinct rates. Scanning force microscopy (SFM) images of the bombarded targets after cooling reveal nanometer-sized craters and/or raised regions (hillocks) around the point of each ion impact. The size of the craters is independent of the temperature for −196 ° C ° C , but for higher temperatures, crater dimensions increase steeply and no hillock is observed behind the crater. The temperature above which the hillocks disappear is sensitive to the cooling rate and for rapidly cooled targets it is near the tabulated value for the glass transition temperature, Tg, of the polymer. Since the variation of the morphology of ion-induced defects occurs over a narrow temperature range and depends on the cooling rate of the targets, single ion bombardment coupled to SFM may be used as an alternative method to estimate Tg and relaxation rates of nanodeformations in thin polymer films. The post-irradiation thermal annealing of the surface tracks produced at room temperature is also discussed.

Damage and ageing effects on proton beam irradiated C60 films

Abstract In this paper, we report results on the interaction of 400 keV H + ions with thin C 60 films focusing on post-irradiation ageing effects. Infrared spectroscopy and resonant α-scattering have been used for characterization of the targets. The analysis were made at different times after bombardment during a period of several months. It has been observed that the signal from the characteristic C 60 IR bands decrease up to 50–70% after the first post-irradiation analysis of the targets. Such ageing is correlated to the appearance and evolution of the oxygen signal in the resonant α-scattering spectra, as well as to the presence of carbonyl bands in the IR spectra of aged targets. For a fixed ageing time the intensity of C 60 IR bands decrease exponentially as a function of fluence.

Etching kinetics of swift heavy ion irradiated silicone rubber with insoluble additives or reaction products

Abstract It is normally understood as a basic precondition of the etching of swift heavy ion tracks in polymers that both the additives and etching products are soluble in the etchant. If this is not given, the polymer surface may be gradually blocked by the deposition of the insoluble material that acts as a diffusion barrier for the penetration of fresh etchant into the tracks, and therefore the effective track etching speed will gradually be reduced. The etching kinetics is developed for that case, and the theory is compared with first experimental findings. For that purpose we have taken commercial silicone rubber foils as test materials, that were irradiated with GeV heavy ions through a mask at a fluence that corresponds to the onset of track overlapping. After etching with NaOH, the corresponding etching speed was recorded via the reduction of the foil thickness. The etching speed is seen to decrease with exposure time, in parallel to the development of an insoluble surface layer. It is discussed how to prevent that surface blocking, to maintain a high etching speed.