Fast Surface Dynamics on a Metallic Glass Nanowire

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Surface dynamics in glasses can significantly differ from bulk behavior, often exhibiting accelerated motion.
• Understanding these surface dynamics is crucial for applications involving thin films and interfaces.

Purpose of the Study:

• To investigate the surface dynamics of a platinum-based metallic glass using high-resolution electron correlation microscopy.
• To quantify the suppression of the glass transition temperature at the surface and the effect of surface coatings on dynamics.

Main Methods:

• Utilized electron correlation microscopy with sub-nanometer resolution to probe surface dynamics.
• Performed parallel molecular dynamics simulations on Ni80P20 to complement experimental findings.
• Investigated the impact of amorphous carbon coatings and chemically binding capping layers on surface dynamics.

Main Results:

• Observed an approximately 20 K suppression of the glass transition temperature at the metallic glass surface.
• Demonstrated that a thin amorphous carbon coating suppresses the enhanced surface dynamics.
• Molecular dynamics simulations confirmed the temperature suppression and showed that a chemically binding capping layer arrests enhanced surface dynamics.
• Identified atomic caging and hopping as mechanisms for near-surface mobility, correlated with cage-breaking barriers and cooperative stringlike motion.

Conclusions:

• Surface dynamics in metallic glasses are significantly enhanced compared to the bulk, evidenced by a lower glass transition temperature.
• Surface coatings, particularly those that chemically bind, can effectively arrest these enhanced dynamics.
• The findings provide fundamental insights into the mechanisms governing atomic mobility at glass surfaces and interfaces.