Transmission imaging with a programmable detector in a scanning electron microscope.

A new type of angularly selective electron detector for use in a scanning electron microscope is presented. The detector leverages a digital micromirror device (DMD) to take advantage of the benefits of two-dimensional (2D) imaging detectors and high-bandwidth integrating detectors in a single optical system. The imaging detector provides direct access to the diffraction pattern, while the integrating detector can be synchronized to the microscope scan generator providing access to a real space image generated by integrating (pixel-by-pixel) a portion of the diffraction pattern as quantitatively defined by the DMD. The DMD, in effect, takes the place of the objective aperture in a transmission electron microscope (TEM) or an annular detector in a scanning transmission electron microscope (STEM), but has the distinct advantage that it can be programmed to take any shape in real time. Proof-of-principle data collected with the detector show diffraction contrast in samples ranging from a polycrystalline gold film to monolayer graphene.