Mn segregation in Ge/Mn5Ge3 heterostructures: The role of surface carbon adsorption

Mn5Ge3 compound, with its room-temperature ferromagnetism and possibility to epitaxially grow on Ge, acts as a potential spin injector into group-IV semiconductors. However, the realization of Ge/Mn5Ge3 multilayers is highly hampered by Mn segregation toward the Ge growing surface. Here, we show that adsorption of some monolayers of carbon on top of the Mn5Ge3 surface prior to Ge deposition allows to greatly reduce Mn segregation. In addition, a fraction of deposited carbon can diffuse down to the underneath Mn5Ge3 layers, resulting in an enhancement of the Curie temperature up to similar to 360 K. The obtained results will be discussed in terms of the formation of a diffusion barrier by filling interstitial sites of Mn5Ge3 by carbon. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3651488]