Ion Track Etching Revisited: Influence of Aging on Parameters of Irradiated Polymers as Required for Advanced Devices

Aging of polymers might contribute to possible malfunction of devices based on them, such as biosensors and others. As hitherto still little is known about the influence of aging on pristine and swift heavy ion-irradiated polymer foils, we had recently started with the re-examination of the etching behaviour and the electronic properties of such materials, which had been subjected to ageing for up to ∼20 years. For this sake, we correlated the as-measured and normalized onset times of etching and etching speeds of the various etching stages with each other. As expected, the sample aging affects the magnitude of these parameters. Surprisingly, this aging effect also differs on both sides of a given sample. The etching parameters were found to correlate not only with both the thickness and the surface roughness of the examined foil samples, but also with the fluence during the ion irradiation. All these effects can be understood easily within a consistent model. As for some examinations, very long etching times were required, the question arose how interruptions during the track etching procedure might affect the final result. In the appendix it is shown that transient sample drying is the safest way to avoid disturbances or falsifications of the measurements.