Nucleation on a stepped surface with an Ehrlich-Schwöbel barrier

Area of Science:

• Surface Science
• Materials Science
• Computational Physics

Background:

• Thin film growth and nucleation dynamics are crucial for material properties.
• Surface morphology, including terrace width and step edges, significantly influences growth modes.
• Understanding nucleation on stepped surfaces is key to controlling thin film fabrication.

Purpose of the Study:

• To investigate the influence of temperature, deposition rate, and terrace width on nucleation during deposition on stepped surfaces.
• To determine the critical monomer density for nucleation and its dependence on terrace width.
• To compare kinetic Monte Carlo (kMC) simulation results with analytical models and experimental data.

Main Methods:

• Kinetic Monte Carlo (kMC) simulations were employed to model deposition on stepped surfaces.
• Analytical steady-state and time-dependent models were used for comparison.
• The influence of the Ehrlich-Schwöbel barrier on nucleation was analyzed.

Main Results:

• Critical nucleation density decreases with increasing terrace width, leading to nucleation at surprisingly low monomer densities.
• Both kMC simulations and analytical models predict a dependence of critical width on diffusion and deposition rate as wc ~ (D/F)^(1/5).
• The Ehrlich-Schwöbel barrier has a limited influence on nucleation unless it falls below a critical value (ΔE(c)(ES)/k(B)T ~ 7.3).

Conclusions:

• A semi-empirical formula was derived to describe nucleation and step-flow growth based on terrace width, diffusion, and deposition rate.
• The study provides insights into controlling nucleation density and growth modes on stepped surfaces.
• The findings are relevant for optimizing thin film deposition processes.