Nowa metoda pomiaru lepkości ultracienkich warstw polimerów

W artykule przedstawiono nową, metodę pomiaru lepkości ultracienkich warstw polimerów. Polega ona na zanurzeniu w warstwie drgającej sondy pomiarowej. Na podstawie zmian częstotliwości rezonansowej oraz fazy jej drgań można wyznaczyć wartość lepkości w funkcji głębokości zanurzenia. Grubość najcieńszej przebadanej warstwy wynosiła 30 nm, a dokładność pomiaru lepkości około 10%. Otrzymane wyniki są zgodne z przewidywaniami oraz z wynikami otrzymywanymi innymi metodami. Nowa metoda pomiarowa może być przydatna w rozwoju nowych technologii takich jak proces nanoimprint lithography.

A new method of measurement viscosity of thin polymeric films is presented. The probe, which is placed on the end of the arm of the mini tuning fork (Fig. 2) is made to oscillate and than is put into the PMMA (poly(methyl methacrylate)) films. Because of the rheological properties of measured samples, the amplitude and resonant frequency are changed. Simple mathematical model of probe, which is immersed partially into a liquid and oscillates, was elaborated. Thirteen samples were examined which differed from each other by the thickness of the film and the molecular weight. The thickness of the films is from 30 nm up to 1080 nm (Tab. 1). All measured properties are depended on temperature, thickness of the film, the depth of indentation of the probe and the molecular weight of PMMA. The viscosity is lower in higher temperatures (Fig. 5) but higher with bigger molecular weight (Fig. 6). They are also lower for thicker films. The results gained from this experiment may be useful in development of nanoimprint lithography and many other branches of nanotechnology. What is more, the method gives a possibility of fast and precise measure-ment of rheological properties of many different thin films in function of temperature.