Design of a TEM/STEM Auger Detector

Abstract

In order to perform surface studies in an electron microscope, one has to be able to detect atoms adsorbed on the surface. The standard approach in surface science is to attach an Auger spectrometer using a CMA or CHA, but such an instrument is intrinsically incompatible with the performance of a TEM/STEM. In this note we describe a design which uses a far smaller analyzer which should be compatible with almost all microscopes.One important aspect of the design is to recognize that due to the strong magnetic lenses, low energy electrons are refocussed along the optic axis of the microscope, based on our trajectory calculations. As an example, Figure 1 shows the calculated trajectories for 500 eV electrons through the upper pole piece of the UHV-H9000 microscope. Figure 2 shows a graph of the final focus position as a function of energy, from which it is apparent that for most energies a final focus occurs between 5mm to 9mm from the specimen;