Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision

Area of Science:

• Surface Science
• Materials Science
• Nanotechnology

Background:

• Helium Ion Microscopy (HIM) offers high resolution and surface sensitivity.
• Understanding surface alloys is crucial for catalysis and electronics.

Purpose of the Study:

• To investigate a surface-confined silver on platinum(111) alloy using HIM.
• To characterize the alloy's structure, work function variations, and periodicity.

Main Methods:

• Helium Ion Microscopy (HIM) for surface imaging and work function analysis.
• Dechanneling contrast in HIM to measure alloy periodicity.
• Comparison with Low Energy Electron Microscopy (LEEM) and Phase Contrast Atomic Force Microscopy (PC-AFM).

Main Results:

• Distinguished Pt-rich and Pt-poor areas based on work function changes (25 meV).
• Visualized atomic layer steps on the Pt(111) surface.
• Measured a periodicity of 6.65 nm for the hcp/fcc pattern in the Ag/Pt alloy along the ⟨112⟩ direction.
• Observed atomic precision coincidence between Ag and Pt lattices (23 Ag atoms on 24 Pt atoms).

Conclusions:

• HIM is effective for atomic-scale characterization of surface alloys.
• The study precisely determined the structural periodicity and atomic arrangement of the Ag/Pt alloy.
• Findings align with complementary microscopy techniques, validating the results.