Loss of control in pattern-directed nucleation: a theoretical study

TL;DR

This paper investigates the transition from controlled to uncontrolled nucleation in pattern-directed processes using kinetic Monte Carlo simulations and analytical models, revealing complex dependencies on system parameters.

Contribution

It provides a combined simulation and analytical study of nucleation control loss near the transition, including detailed microscopic insights and model comparisons.

Findings

Nucleation control is lost due to complex parameter dependencies.

Stationary concentration fields help predict nucleation probabilities.

Analytical models can rationalize simulation results.

Abstract

The properties of template-directed nucleation are studied close to the transition where full nucleation control is lost and additional nucleation occurs beyond the pre-patterned regions. First, kinetic Monte Carlo simulations are performed to obtain information on a microscopic level. Here the experimentally relevant cases of 1D stripe patterns and 2D square lattice symmetry are considered. The nucleation properties in the transition region depend in a complex way on the parameters of the system, i.e. the flux, the surface diffusion constant, the geometric properties of the pattern and the desorption rate. Second, the properties of the stationary concentration field in the fully controlled case are studied to derive the remaining nucleation probability and thus to characterize the loss of nucleation control. Using the analytically accessible solution of a model system with purely radial symmetry, some of the observed properties can be rationalized. A detailed comparison to the Monte Carlo data is included.