Sublayer-Enhanced Growth of Highly Ordered MnGe Thin Film on Si(111).

MnGe epitaxial thin films previously grown mainly on Ge substrate have been synthesized on Si(111) using the co-deposition of Mn and Ge at a temperature of 390 °C. RMS roughness decreases by almost a factor of two in the transition from a completely polycrystalline to a highly ordered growth mode. This mode has been stabilized by changing the ratio of the Mn and Ge evaporation rate from the stoichiometric in the buffer layer. Highly ordered MnGe film has two azimuthal crystallite orientations, namely MnGe (001) [1-10] and MnGe (001) [010] matching Si(111)[-110]. Lattice parameters derived (7.112(1) Å) and (5.027(1) Å) are close to the bulk values. Considering all structural data, we proposed a double buffer layer model suggesting that all layers have identical crystal structure with P6₃/mcm symmetry similar to MnGe, but orientation and level of Si concentration are different, which eliminates 8% lattice mismatch between Si and MnGe film. MnGe film on Si(111) demonstrates no difference in magnetic properties compared to other reported films. T is about 300 K, which implies no significant excess of Mn or Si doping. It means that the buffer layer not only serves as a platform for the growth of the relaxed MnGe film, but is also a good diffusion barrier.