Roughness and Correlations in the Transition from Island to Film Growth: Simulations and Application to CdTe Deposition

TL;DR

This paper uses kinetic Monte Carlo simulations to connect microscopic dynamics with surface morphology during island and film growth, applying the framework to CdTe deposition to analyze roughness evolution and estimate diffusion coefficients.

Contribution

The study introduces a simulation-based framework linking island growth dynamics, roughness, and Ehrlich-Schw"obel barriers, with application to real CdTe deposition data.

Findings

Island width is controlled by adatom mobility.

Lower Ehrlich-Schw"obel barrier delays coalescence and increases roughness.

Maximum roughness during coalescence indicates negligible Ehrlich-Schw"obel barrier.

Abstract

Using kinetic Monte Carlo simulations, we develop a framework to relate morphological properties and microscopic dynamics during island growth, coalescence, and initial formation of continuous heteroepitaxial films. The average island width is controlled by adatom mobility on the substrate. Subsequent evolution strongly depends on the Ehrlich-Schw\"{o}ebel energy barrier $E_{ES}$ of the deposited material. As $E_{ES}$ decreases, islands becomes taller and their coalescence is delayed. For small islands and large $E_{ES}$, the global roughness increases as $W\sim{\text{thickness}}^{1/2}$ and the local roughness increases at short scales (apparent anomalous scaling) before and after island coalescence. If the islands are wide, $W$ may have a plateau for large $E_{ES}$ and has a maximum for small $E_{ES}$ when the islands coalesce. This framework is applied to atomic-force microscopy data of the initial stages of CdTe deposition on Kapton: a maximum of $W$ during island coalescence indicates negligible ES barrier, consistently with scaling properties of much thicker films, and the diffusion coefficient ${10}^{-7}{\text{--}}{10}^{-5}{\text{cm}}^2/{\text s}$ on the Kapton surface at $150\,^{\circ}\mathrm{C}$ is estimated. Applications of the framework to other materials are suggested, in which the expected roles of ES barriers are highlighted.