Demonstration of Solid State Electron Optical Devices: Pixelated Fresnel Phase Lenses

Abstract

The ability to produce features of nanometer scale offers the possibility of phase manipulation of electron waves. The first conclusive results of phase manipulation by nanometer-scale diffraction gratings directly cut by the finely focused electron beam in a scanning transmission electron microscope (STEM) have already been demonstrated. This was achieved by using a grating with a “wedge” profile. This produced an asymmetrical diffraction pattern (in violation of Friedel's law). This violation is expected only if the grating acts mostly as a strong phase object. In this paper, a demonstration of solid state Pixelated Fresnel Phase (PFP) lenses for electrons will be presented. An array of these electron lenses can be easily formed and may be utilized, for example, as compact electron-beam forming lenses for parallel electron beam lithography.In general, an incident plane wave traveling along the optic axis of a lens experiences a phase shift. A conventional Fresnel phase lens, consisting of concentric zones with a modulo of 2π phase structure, focuses an incoming electron plane wave to its focal point.