Growth competition between semiconducting Ge1−xMnx nanocolumns and metallic Mn5Ge3 clusters

Thi-Giang Le, Minh-Tuan Dau, Vinh Le Thanh, D N H Nam, Matthieu Petit, Lisa A Michez, Van-Khiem Nguyen and Manh-An Nguyen

Abstract

Structural and magnetic characterizations have been combined to investigate the growth kinetics of Ge_1−xMn_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−xMn_x 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