How to image single isolated atoms by using coherent low-energy electrons

Area of Science:

• Atomic and Molecular Physics
• Electron Microscopy
• Surface Science

Background:

• Coherent low-energy electrons are effective for imaging macromolecules and 2D crystals.
• Low-energy electrons offer reduced radiation damage and high sensitivity to local potentials.

Purpose of the Study:

• To determine the conditions for imaging single, isolated, charge-free atoms using low-energy electron holography.
• To analyze the interference patterns produced by single atoms.

Main Methods:

• Utilizing low-energy electron holography to probe single atoms.
• Analyzing the interference patterns, specifically the diffraction angle (θ) from concentric fringes.
• Investigating the relationship between diffraction angle and source-to-sample distance (zs).

Main Results:

• A single atom generates a weak interference pattern of concentric fringes.
• The diffraction angle (θ) follows the relationship sin(θ) ∼ 0.3/zs^(1/2).
• This dependency holds for various electron energies (50-200 eV) and elements (Li, C, Cs).

Conclusions:

• Low-energy electron holography is a viable method for imaging individual atoms.
• The observed diffraction angle dependency provides a quantitative understanding of the imaging process.
• Results are consistent with experimental observations of alkali atoms on graphene.