Growth competition between semiconducting Ge1-x Mnx nanocolumns and metallic Mn5Ge3 clusters
Résumé
Structural and magnetic characterizations have been combined to investigate the growth
kinetics of Ge 1−x Mn x diluted magnetic semiconductors (DMSs) on Ge(001) substrates by
means of molecular beam epitaxy (MBE). We have identified the growth process window
allowing stabilization of a high Curie temperature (T C ) nanocolumn phase and provide
evidence that the growth of semiconducting Ge 1−x Mn x nanocolumns and metallic Mn 5 Ge 3
clusters is a competing process. Due to a continuous increase of the Mn concentration inside
nanocolumns, induced by Mn segregation along the growth direction from the interface toward
the film surface, nanocolumns become unstable when the Mn concentration reaches a value of
∼40 at.% then transform into Mn 5 Ge 3 clusters. We propose a real-time approach to realize
stacked layers consisting of nanocolumns separated by a Ge barrier layer, allowing
exploitation of the effect of giant magneto-resistance in multilayer structures