Real-space study of the growth of magnesium on ruthenium

► Layer-by-layer growth of Mg/Ru(0001) studied by LEEM and STM. ► Observed oscillations in the electron reflected intensity as a function of thickness. ► LEED in LEEM shows in-plane spacing changes with sub-monolayer coverage. ► On films several ML thick stacking faults and screw dislocations are observed. ► Screw dislocations are caused by the mismatch in heights of the Mg and Ru steps.