Optimizing phase contrast in transmission electron microscopy with an electrostatic (Boersch) phase plate

Area of Science:

• Electron Microscopy
• Phase Contrast Imaging
• Nanofabrication

Background:

• Conventional transmission electron microscopy (TEM) struggles with low contrast for weak amplitude and phase objects like unstained biological samples.
• Phase contrast light microscopy utilizes quarter-wave phase plates to enhance weak phase object imaging.
• Previous attempts to create an analogous electron microscope phase plate using an electrostatic einzel lens were hindered by device size.

Purpose of the Study:

• To fabricate and apply a miniaturized electrostatic einzel lens as a transmission electron microscopy (TEM) quarter-wave phase plate.
• To improve contrast in imaging weak phase objects using TEM.
• To overcome the limitations of previous einzel lens designs for phase plate applications.

Main Methods:

• Fabrication of a microstructured electrostatic einzel lens acting as a TEM quarter-wave phase plate.
• Generation of phase modulation via an electrostatic field confined within a microstructured ring electrode.
• Adjustment of the phase shift of the primary electron beam to pi/2.

Main Results:

• Successful fabrication and application of a miniaturized electrostatic einzel lens as a TEM quarter-wave phase plate.
• Achieved strong phase contrast independent of spatial frequency by adjusting the phase shift to pi/2.
• Demonstrated mechanical stability and preservation of high-resolution image quality without significant residual lens effects.
• Utilized a threefold symmetry arrangement of supporting rods for optimized single-sideband signal transfer.

Conclusions:

• The developed miniaturized electrostatic einzel lens effectively functions as a TEM quarter-wave phase plate.
• This technology offers a viable solution for high-contrast imaging of weak phase objects in biological electron microscopy.
• The design ensures mechanical stability and maintains high-resolution imaging capabilities.