Real-space study of the growth of magnesium on ruthenium

TL;DR

This study investigates the growth mechanisms and structural properties of magnesium on ruthenium using LEEM and STM, revealing layer-by-layer growth, moiré patterns, stacking faults, and quantum size effects.

Contribution

It provides detailed real-space imaging and analysis of Mg growth on Ru, highlighting the formation of moiré patterns, defects, and quantum oscillations at the interface.

Findings

Layer-by-layer Mg growth observed up to 10 ML.

Moiré pattern with 1.2 nm periodicity at sub-monolayer coverage.

Quantum size effect oscillations indicate an abrupt Mg/Ru interface.

Abstract

The growth of magnesium on ruthenium has been studied by low-energy electron microscopy (LEEM) and scanning tunneling microscopy (STM). In LEEM, a layer-by-layer growth is observed except in the first monolayer, where the completion of the first layer in inferred by a clear peak in electron reflectivity. Desorption from the films is readily observable at 400 K. Real-space STM and low-energy electron diffraction confirm that sub-monolayer coverage presents a moir\'e pattern with a 1.2 nm periodicity, which evolves with further Mg deposition by compressing the Mg layer to a 2.2 nm periodicity. Layer-by-layer growth is followed in LEEM up to 10 ML. On films several ML thick a substantial density of stacking faults are observed by dark-field imaging on large terraces of the substrate, while screw dislocations appear in the stepped areas. The latter are suggested to result from the mismatch in heights of the Mg and Ru steps. Quantum size effect oscillations in the reflected LEEM intensity are observed as a function of thickness, indicating an abrupt Mg/Ru interface.