Elemental mapping using the Ga 3d and In 4d transitions in the ε2 absorption spectra derived from EELS

It is proposed that by using the valence–band states in electron energy loss spectroscopy, high-spatial resolution maps of quantitative elemental composition may be acquired with high acquisition rates. Further, it is shown that by using the ε2 spectrum instead of single scattering data, the noise in the observed transitions and associated maps is significantly reduced. The ε2 spectra are derived through a Kramers–Kronig transformation from electron energy loss spectra obtained in a scanning transmission electron microscope. Using transitions that occur in the ε2 absorption spectrum (<40 eV), quantitative elemental maps for III–V device structures have been produced. An example is provided using the Ga 3d transition to map a GaInNAs/GaAs laser structure. Weaker transitions such as In 4d have also been used to verify the Ga elemental distribution.