A LEED study of NO superstructures on the Pd(111) surface

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Nitrogen monoxide (NO) adsorption on metal surfaces is crucial for catalysis.
• Understanding surface structures and transformations is key to controlling chemical reactions.

Purpose of the Study:

• To investigate two specific adsorption structures of NO on the Pd(111) surface.
• To analyze the structural transformation between these NO/Pd(111) surface phases.

Main Methods:

• Acquisition and analysis of Low-Energy Electron Diffraction (LEED) I(V) curves.
• Utilized tensor LEED for detailed structural modeling.
• Confirmed findings with previous scanning tunneling microscopy and DFT studies.

Main Results:

• Characterized the Pd(111)-p(2 × 2)-NO and Pd(111)-c(4 × 2)-NO structures.
• The c(4 × 2)-NO structure (0.5 ML) features NO in hollow sites with slight tilting.
• The p(2 × 2)-NO structure (0.75 ML) shows NO in hollow and on-top sites with significant tilting of the on-top molecule.
• Observed a transition from p(2 × 2) to c(4 × 2) upon heating, linked to NO thermal desorption and domain walls.

Conclusions:

• Structural models for NO adsorption on Pd(111) were confirmed.
• NO-NO repulsion may influence molecular tilting in the c(4 × 2) structure.
• The heating-induced phase transition provides insights into surface dynamics and domain wall behavior.