Oxidation-driven surface dynamics on NiAl(100)

Area of Science:

• Materials Science
• Surface Science
• Physical Chemistry

Background:

• Atomic steps are inherent defects on crystal surfaces influencing physical and chemical processes.
• Predicting surface dynamics under nonequilibrium conditions is challenging due to limited understanding of step-related mass transport.

Purpose of the Study:

• To investigate the role of atomic steps in oxide film growth dynamics.
• To elucidate the mechanisms of surface motion and mass transport during oxidation and decomposition of NiAl(100).

Main Methods:

• Utilized low-energy electron microscopy (LEEM) for spatially and temporally resolved observation.
• Studied the oxidation of NiAl(100) single crystal surfaces.

Main Results:

• Demonstrated that surface steps are impermeable to oxide film growth on NiAl(100).
• Observed that oxide advancement occurs on terraces, driven by coordinated step migration.
• Found that step accumulation ahead of the growth front impedes oxidation, a process reversed during decomposition.
• Modeled substrate step migration as a Hele-Shaw problem, involving Al atom detachment/attachment at step edges.

Conclusions:

• Oxidation rate is limited by surface step behavior when steps supply atoms.
• When atoms originate from the bulk, oxidation is not limited by surface step motion.
• The findings provide a new understanding of surface-controlled oxidation kinetics.