Abstract

The possibility of designing iron silicide wires along Bi nanolines on the hydrogenated Si(001) surface is addressed by spin-density functional calculations. We study plausible adsorption sites for various submonolayer (ML) coverages of Fe atoms along the nanolines. It is found that for a lower coverage of 1/8 ML, Fe atoms are adsorbed beside the Bi nanoline forming sevenfold coordinate structures with the Si subsurface layer. For 1/4 ML coverage, Fe atoms form a linear chain parallel to the nanolines with a semiconducting character, whereas for 1/2 ML coverage they form a zigzag chain with a metallic character. For the increased coverage of 3/4 ML the metallic character is maintained and the Fe atoms are accommodated between the second- and third-Si layers. The calculated formation energy of Fe adatoms decreases with increasing coverage, supporting the formation of iron silicide wire parallel to the Bi nanolines. In addition, for Fe coverages higher than 1/4 ML, the systems exhibit weak antiferromagnetic states which are almost energetically degenerated with their respective nonmagnetic states, suggesting that Fe adatoms have their magnetism quenched as the Fe wire forms. Finally, the orbital and electronic distribution of Fe adatoms on the Bi nanolines is analyzed in term of simulated STM images. © 2008 The American Physical Society.