Growth competition between semiconducting Ge1-x Mnx nanocolumns and metallic Mn5Ge3 clusters

Structural and magnetic characterizations have been combined to investigate the growthkinetics of Ge 1−x Mn x diluted magnetic semiconductors (DMSs) on Ge(001) substrates bymeans of molecular beam epitaxy (MBE). We have identified the growth process windowallowing stabilization of a high Curie temperature (T C ) nanocolumn phase and provideevidence that the growth of semiconducting Ge 1−x Mn x nanocolumns and metallic Mn 5 Ge 3clusters is a competing process. Due to a continuous increase of the Mn concentration insidenanocolumns, induced by Mn segregation along the growth direction from the interface towardthe 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 realizestacked layers consisting of nanocolumns separated by a Ge barrier layer, allowingexploitation of the effect of giant magneto-resistance in multilayer structure