Secondary electron imaging of nonconductors with nanometer resolution

The resolution of secondary electron (SE) images in scanning electron microscopy (SEM) is limited by the SE diffusion length. However, most materials are poor electrical conductors and in practice, resolution and image information content are often limited by charging. We demonstrate how charging can be eliminated as the resolution-limiting factor using a gaseous SE detector for magnetic immersion electron lenses. Charging is stabilized by ions produced in a magnetic field-assisted gas ionization cascade. The charge control self-regulation process does not quench the SE imaging signal, thereby enabling high resolution image contrast mechanisms that are suppressed in high vacuum SEM.