Assessment of Beam Damage in Polymers Caused by in situ ESEM Analysis using IR Spectroscopy

The environmental scanning electron microscope (ESEM) enables in situ analyses of non-conducting samples such as polymers, thus allowing microscopic phenomena to be correlated to macroscopic measurement data. Unfortunately, irradiation of polymers with electrons always causes beam damage1 and it is unclear whether this damage could influence the outcome of the experiments. The amount of beam damage in polymers is mainly determined by the electron dose, which is a function of the probe current, the irradiation time, the irradiated area and the type of imaging gas used. The beam damage during in situ tensile tests of peel films was assessed using Fourier transformed infrared spectroscopy (FTIR). The band at 965 cm⁻¹ turned out to be significant for the estimation of beam damage in this material, which was verified by long-term measurements. The measurements were performed in an ESEM Quanta 600 FEG at parameters comparable to the prior in situ tensile tests. Additional measurements were performed in a Quanta 200 at parameters typical of in situ investigations. Again, the out-of-plane trans ==C---H wag at 965 cm⁻¹ turned out to be significant for beam damage and was used as an indicator for beam damage (dehydrogenation) for this type of material.