Interdiffusion in Heusler film epitaxy on GaAs (001)
Sprache des Vortragstitels:
Ferromagnetic layers with a high spin polarization on semiconductor substrates are attracting increasing
interest for applications in spin- and magnetoelectronics. A promising material class are the binary or ternary
Heusler compounds that include also so-called halfmetallic ferromagnets, e. g., Co2FeSi. For attaining high spin
polarization perfect crystallographic order as well as the formation of abrupt and chemically defined interfaces
are essential. According to recent theory, spin-transport across interfaces depends dramatically on the type of
atoms participating in the contact layer with detrimental consequences of interface disorder due to
interdiffusion or interface reactions.
The talk focuses on on interdiffusion processes occurring during molecular beam epitaxy of the binary, thus
experimentally simpler FeSi films on GaAs(001), including the Heusler compound Fe3Si. Our experiments reveal
a strong interdiffusion of Fe and Si into the GaAs substrate as well as of As and Ga into the FeSi films, creating
intermixed layers of 2?3 nm thickness in both, film and substrate. Interdiffusion is dominant already at
moderate growth temperatures required for crystallographic ordering, thus demanding new concepts including
appropriate diffusion barriers for the development for ferromagnet/semiconductor hybrid systems.