Although elements of low atomic number (Z<11) are detectable in TEM specimens using a modem energy-dispersive (EDX) detector, quantification remains a challenge. Problems include the large absorption corrections needed for specimens of typical thickness and the need for calibration specimens which provide k-factors appropriate to a particular detector/window arrangement. We have addressed this second problem by fabricating thin films containing several light elements in combination with silicon, which typically acts as the reference element when specifying k-factors.
Because the EDX peaks of adjacent light elements overlap considerably, it is preferable to have two specimens: one containing C, O and Si, the other B, N, F and Si. We have used both e-beam evaporation and sputtering techniques to deposit thin films on a substrate which can later be removed to leave a freestanding film mounted on a TEM grid.