Shape transitions in strained Cu islands on Ni(100): kinetics versus energetics

Area of Science:

• Surface science
• Materials science
• Thin film growth

Background:

• Submonolayer copper (Cu) deposition on nickel (Ni)(100) surfaces exhibits complex ramified island structures.
• Understanding the factors governing island shape evolution is crucial for controlling thin film morphology and properties.

Purpose of the Study:

• To investigate the energetic and kinetic contributions to the observed ramified island shapes in Cu/Ni(100) growth.
• To elucidate the underlying mechanisms responsible for the transition in island morphology.

Main Methods:

• Utilized accelerated dynamics simulations to explore island energy dependence on shape.
• Employed Kinetic Monte Carlo (KMC) simulations incorporating concerted popout processes at step edges.
• Compared simulation results with experimental observations of island shapes.

Main Results:

• Strain-energy contributions to island shape were found to be unexpectedly weak.
• Accelerated dynamics simulations identified concerted popout processes at step edges as a significant factor.
• KMC simulations including these kinetic processes accurately reproduced experimentally observed island shapes.

Conclusions:

• The observed island shape transition in Cu/Ni(100) growth is primarily of kinetic origin.
• Strain plays a mediating role in the kinetic processes governing island morphology.
• Concerted popout events at step edges are key to understanding ramified island formation.