Sub-ångström resolution ptychography in a scanning electron microscope at 20 keV

Area of Science:

• Materials Science
• Physics
• Microscopy

Background:

• Sub-ångström resolution in electron microscopy typically requires expensive, high-energy transmission electron microscopes (TEMs).
• Low-energy scanning electron microscopes (SEMs) offer a more accessible and cost-effective alternative.
• Lower beam energies can enhance information retrieval from light-element samples.

Purpose of the Study:

• To demonstrate sub-ångström resolution using a low-energy scanning electron microscope.
• To explore the potential of ptychographic reconstruction for enhancing SEM resolution.
• To provide a more accessible method for high-resolution imaging.

Main Methods:

• Utilized a 20 keV scanning electron microscope (SEM) operated in transmission mode.
• Employed a multi-slice ptychographic reconstruction algorithm with diffraction distortion correction.
• Integrated a cold field emission source, immersion lens, projector lens, and a specialized detector for low-energy electrons.

Main Results:

• Achieved a sub-ångström resolution of 0.67 Å, a resolution-to-wavelength ratio of 7.8.
• Surpassed previous resolution records in electron ptychography and conventional imaging.
• Demonstrated the efficacy of the developed ptychographic algorithm and SEM configuration.

Conclusions:

• Low-energy SEMs, when combined with advanced ptychographic reconstruction, can achieve sub-ångström resolution.
• This technique offers a more affordable and compact solution for high-resolution electron microscopy.
• Potential applications include imaging 2D materials and structural studies of proteins.