Resolving sub-nm steps with a low-voltage miniature scanning electron microscope

Abstract

Miniature scanning electron beam columns based on silicon microfabricated components and Schottky field-emission sources have been recently developed and deployed in commercial field-emission scanning electron microscopes. A second generation column, optimized for low-voltage imaging, was used to image defects in 6 H-SiC using topographic mode. By comparing specific regions with AFM, steps of ∼0.8 nm could be identified. The images obtained with this technique are consistent with electron channeling contrast imaging (ECCI) but at significantly lower voltage, from 500 eV to 1.2 keV. The geometry of the detector, the collection angle, the beam convergence angle, and the source characteristics are consistent with optimum conditions for normal incidence ECCI.