An energy dependent model for type I magnetic contrast in the scanning electron microscope

Abstract

The modelling of the magnetic contrast phenomenon in the scanning electron microscope (SEM) is important in understanding the physics of the contrast mechanism and the associated signal detection. In this paper, we report an improved analytical model for Type I magnetic contrast calculations using an approximate form of the Chung and Everhart secondary electron (SE) energy distribution. Previous studies have neglected this factor by assuming a mono- energetic model in order to simplify the calculations. This new model can be used to study different material specimens by appropriate choice of the work function and field-distance integral. The effect of energy filtering on the Type I magnetic contrast and quality factor can also be studied with the improved model by substituting the low and high energy limits of the filtered SE distribution into the closed-form analytical expressions obtained. Results of the above-mentioned effects and the effect of collector aperturing are reported in this paper using the new improved energy dependent model.