Design of a microfabricated, two-electrode phase-contrast element suitable for electron microscopy

Area of Science:

• Electron microscopy
• Phase contrast imaging
• Microfabrication

Background:

• Achieving Zernike-type, in-focus phase contrast in electron microscopes is crucial for high-resolution imaging.
• Conventional methods often involve complex designs and fabrication processes.

Purpose of the Study:

• To design and demonstrate a miniature electrostatic element for selective phase shifting in electron microscopes.
• To realize Zernike-type, in-focus phase contrast with a simplified approach.

Main Methods:

• Design of a cylindrical, biased-voltage electrode surrounded by a concentric grounded electrode.
• Electrostatic calculations to analyze fringing field effects on scattered electron beams.
• Microfabrication of the electrostatic element with feature sizes around 1 micrometer.
• Experimental verification of the 90-degree phase shift capability.

Main Results:

• The electrostatic element selectively applies a 90-degree phase shift to the unscattered beam.
• Fringing fields cause negligible phase shifts for scattered beams when electrode length to feature size ratio is > 5:1.
• The design avoids insulating layers, enabling simple microfabrication.
• Mechanically robust devices with ~1 micrometer feature sizes were successfully fabricated.
• Preliminary experiments confirmed the intended phase shift between scattered and unscattered electrons.

Conclusions:

• The developed miniature electrostatic element effectively achieves Zernike-type, in-focus phase contrast.
• This simplified microfabrication process offers a practical advancement for electron microscopy.
• The device shows potential for routine application in phase contrast imaging.