Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 10: Semiconductor surfaces and interfaces
O 10.2: Vortrag
Montag, 27. März 2006, 15:15–15:30, PHY C213
Morphology of ultrathin manganese silicide films on Si(001) and Si(111) substrates — •Mahbube Hortamani, Peter Kratzer, and Matthias Scheffler — Fritz-Haber Institut, Faraday weg 4-6, 14195 Berlin, Germany
Recently, the field of spintronics has attracted much attention since it provides knowledge for a novel type of electronic devices that use the electron’s spin, in addition to its charge, for processing and storage of data. Ferromagnetic metal/semiconductor interfaces hold great promise for fabrication of such devices. Covering Si with a layer of Mn intermetallic compounds is one possibility to produce such interfaces. We investigate the stability of MnxSiy films on Si for various stoichiometries and atomic structures of the films, using density functional theory with the GGA-PBE functional and the FP-APW+lo method. We find that for ultrathin film growth on the Si substrate, the manganese-silicon multilayers with 1:1 stoichiometry (MnSi) are more stable than a pure Mn film or other silicide compounds. The formation of the B20 structure on the Si(111) substrate is found to be thermodynamically more stable than films of other structures. While the B20 structure is not compatible with the Si(001), we suggest a closly lattice-matched B2 structure to form on this surface. By simulating the proposed B2 structure on both (001) and (111) surfaces, we find that the film formation on Si(111) is energetically favorable. However, the films on Si(001) are metastable compared to formation of MnSi islands, and hence Volmer-Weber growth is expected. In all MnSi films on Si(111) the Mn atoms in the interface and surface layer have sizable magnetic moments.