Advances in Natural Sciences: Nanoscience and Nanotechnology OPEN ACCESS Growth competition between semiconducting Ge1−xMnx nanocolumns and metallic Mn5Ge3 clusters

Structural and magnetic characterizations have been combined to investigate the growth kinetics of Ge1−xMnx 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 (TC) nanocolumn phase and provide evidence that the growth of semiconducting Ge1−xMnx nanocolumns and metallic Mn5Ge3 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 Mn5Ge3 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