Mg/Si(100) reconstructions studied by scanning tunneling microscopy

Using scanning tunneling microscopy (STM), the behavior of Mg submonolayers on a Si(100)2 x 1 surface has been studied during deposition at roam tempe rature (RT) and upon annealing at 250 degrees C and 400 degrees C. RT-depos ited Mg forms meandering chains of features that run roughly perpendicular to the substrate Si dimer rows and, at saturation, tend to form the arrays of the 2 x 2 reconstruction. Annealing at 250 degrees C transforms the chai ns to random groups of Mg clusters. Subsequent annealing at 400 degrees C i nduces Si redistribution at the surface and results in the formation of str aight chains of features that are again aligned perpendicular to the Si dim er rows. These high-temperature (HT) features are plausibly composed of 1 S i atom and 1-2 Mg atoms. The spacing of the HT features within the chain is 2a (a = 3.84 Angstrom) and stacking of the chains produces the domains of 2 x 2, 2 x 3 and other 2 x n reconstructions. At saturation, almost the ent ire surface is occupied by the 2 x 2 reconstruction. At higher Mg coverages , the growth of a silicide occurs both at RT deposition and upon annealing.