Measuring the Thickness of Aluminium Alloy Thin Foils Using Electron Energy Loss Spectroscopy

Combining electron energy loss spectroscopy and convergent beam electron diffraction measurements, we have determined the mean-free-path for inelastic electron scattering for four different aluminium alloys. Electron energy loss spectroscopy spectra were acquired with the transmission electron microscope in image mode, without any objective aperture inserted. The value for pure aluminium was determined as 119 ± 5nm at an incident electron energy of 150keV. For the most common alloys with moderate amounts of alloying elements, no significant changes in the mean-free-path values are measured within the 5% accuracy of the method. The-mean-free path values are required for accurate determination of the thickness of thin foils for transmission electron microscopy using electron energy loss spectroscopy. On the basis of our experimental results, we estimate a single measurement of foil thickness to have an accuracy of better than 8% if the mean-free-path is known within 5%. The outlined procedure for thickness measurements is very robust, with thickness results being insensitive to experimental details such as inclination of the specimen or diffracting conditions.