Technology note discusses details and caveats of nanometer scaled resolution STEM-EDS analysis
The spatial resolution of energy dispersive spectroscopy (EDS) analysis is fundamentally limited by the interaction volume of the characteristic X-ray emission.
Typical EDS analysis in an SEM is performed at relatively high energy (> 10 kV), leading to a huge interaction volume on the order of micrometers. Lowering the energy of the primary electron beam reduces the interaction volume significantly, but brings many practical challenges, including low count rates during analysis.
Achieving nanometer resolution in EDS analysis
An alternative method to reduce the interaction volume is to use a thin sample, on the order of tens of nanometers. The sample is now thin enough to be transparent to the electron beam of a transmission scanning electron microscopy, making STEM-EDS possible.