Phase Plate STEM Imaging Using Two Dimensional Electron Detector

Phase plate (PP) in Scanning Transmission Electron Microscopy (STEM) can modify phase contrast transfer function from sine type to cosine type to enhance phase contrast of biological molecules composed of light elements In phase plate STEM (P-STEM), we used a carbon PP with a center hole (Zernike PP). A mean inner potential of the film material provide a phase shift to the incident electron wave. We adjust the thickness of the carbon film to provide a half phase shift to the electron wave with energy of 200KeV. Since we have to use the unscattered electron wave without phase shift and the scattered waves with phase shift to obtain higher contrast image in P-STEM, a detection aperture to choose electron waves with an appropriate optical condition should be used just above the detector. The electron waves with the appropriate P-STEM condition lands in the circle region indicated with "Out of plane" in Fig.