Measurement of electron beam broadening in stainless steels during EDS analysis in the FEG-TEM

: The effect of electron beam broadening on spatial resolution of EDS analysis in a 200 kV cold-FEG-TEM has been investigated for Type 316L stainless steel. Platinum (Pt) was evaporated on half the 316L TEM foil surface, and the difference in Pt concentration profiles obtained by the EDS method from the Pt evaporated surface and its opposite side was analysed as a function of foil thickness. Advantages of Pt use are that Pt is not included in the 316L steel, and it is easily formed as a stable and continuous thin evaporated film on the stainless steel. No change of spatial resolution caused by electron beam broadening was observed in stainless steel foils of less than about 140 nm thick subjected to EDS analysis with the FEG-TEM (incident probe size 1.6 +/- 0.2 nm diameter). Specimens of about 160 nm and more thick had a decrease in spatial resolution, but the decrease was smaller than that predicted from theoretical calculations of beam broadening for stainless steels. It is suggested that only the central part of the broadened electron beam with high intensity influences the spatial resolution of EDS analysis with the FEG-TEM.