  Mn5Ge3 thin films have been demonstrated as a promising spin-injector
material for germanium-based spintronic devices. So far, Mn5Ge3 has been grown
epitaxially only on Ge (111) substrates. In this letter we present the growth
of epitaxial Mn5Ge3 films on Ge (100) substrates. The Mn5Ge3 film is
synthetized via sub-second solid-state reaction between Mn and Ge upon flash
lamp annealing for 20 ms at the ambient pressure. The single crystalline Mn5Ge3
is ferromagnetic with a Curie temperature of 283 K. Both the c-axis of
hexagonal Mn5Ge3 and the magnetic easy axis are parallel to the Ge (100)
surface. The millisecond-range flash epitaxy provides a new avenue for the
fabrication of Ge-based spin-injectors fully compatible with CMOS technology.
