Optimization of Electrostatic Phase Plate for Biological Specimens in Transmission Electron Microscopy

The inner and outer diameter of electrostatic phase plate d_i, d_m and d_o limit the number of electrons passing through and then affect the high-resolution information in the phase contrast image. The current density contours at the upper surface of the phase plate is first used to determine d_i, d_m and d_o. The current density contours and trajectory of un-scattered electrons under a real objective lens model were simulated by traditional aberration integrated method. The current density contours of scattered electrons were obtained by solving the Newton-Lorentz equation of motion. In building the motion equation in a practical field, second order finite element method and Hermite function interpolation are applied to get the axial field and its arbitrary order. The motion equations were solved by fifth-order Runge-Kutta algorithm and the performance of scattered electrons was given for a 200kV TEM. From our simulation, d_i should be larger than 6.4nm, d_m should be possible enough to be fabricated and d_o be larger than 32¿m.