Surfactant-mediated growth revisited.

Area of Science:

• Materials Science
• Surface Science
• Thin Film Growth

Background:

• Surfactant-mediated epitaxy is crucial for controlling thin film properties.
• Oxygen is often used as a surfactant in metal film growth, particularly for nickel on copper.
• The exact location and role of surfactant atoms during growth are not fully understood.

Purpose of the Study:

• To investigate the precise location of oxygen during nickel growth on Cu(001).
• To clarify the mechanism of oxygen's surfactant action in this system.
• To understand the implications for magnetic anisotropy in nickel films.

Main Methods:

• X-ray structure analysis was employed to determine atomic positions.
• Surface stress measurements were used to corroborate structural findings.

Main Results:

• Oxygen atoms were identified in subsurface octahedral sites, up to 0.15 monolayers.
• This contradicts the traditional model of surfactant oxygen residing solely on the surface.
• An oxygen-enriched zone spanning the top two layers was proposed as the active surfactant region.

Conclusions:

• The surfactant action of oxygen in Ni/Cu(001) growth involves subsurface atoms.
• This revised understanding is critical for optimizing thin film growth processes.
• The findings have significant implications for controlling magnetic anisotropy in nickel-based films.