Scaling of Island Growth in Pb Overlayers on Cu(001)

TL;DR

This study investigates the growth and ordering of Pb islands on Cu(001) at 150 K, revealing a scaling behavior where island size increases with coverage, and most islands nucleate early and grow self-similarly.

Contribution

The paper presents a detailed analysis of island growth scaling laws and introduces a simple model for island growth on Pb/Cu(001) surfaces.

Findings

Island size follows a power law with coverage (exponent ~0.54)

Island density remains approximately constant between 0.1 and 0.5 coverage

Most islands nucleate at coverage below 0.1 and grow self-similarly

Abstract

The growth and ordering of a Pb layer deposited on Cu(001) at 150 K has been studied using atom beam scattering. At low coverage, ordered Pb islands with a large square unit cell and nearly hexagonal internal structure are formed. This is a high order commensurate phase with 30 atoms in the unit cell. From the measurement of the island diffraction peak profiles we find a power law for the mean island - size versus coverage with an exponent $n=0.54 \pm 0.03$. A scaling behavior of growth is confirmed and a simple model describing island growth is presented. Due to the high degeneracy of the monolayer phase, different islands do not diffract coherently. Therefore, when islands merge they still diffract as separate islands and coalescence effects are thus negligible. From the result for $n$ we conclude that the island density is approximately a constant in the coverage range $0.1 < \Theta < 0.5$ where the ordered islands are observed. We thus conclude that most islands nucleate at $\Theta < 0.1$ and then grow in an approximately self similar fashion as $\Theta$ increases.