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

Using scanning tunneling microscopy (STM), the behavior of Mg submonolayers on a Si(100)2×1 surface has been studied during deposition at room temperature (RT) and upon annealing at 250 °C and 400 °C. RT-deposited 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 2×2 reconstruction. Annealing at 250 °C transforms the chains to random groups of Mg clusters. Subsequent annealing at 400 °C induces Si redistribution at the surface and results in the formation of straight chains of features that are again aligned perpendicular to the Si dimer rows. These high-temperature (HT) features are plausibly composed of 1 Si atom and 1-2 Mg atoms. The spacing of the HT features within the chain is 2a (a = 3.84 angstroms) and stacking of the chains produces the domains of 2×2, 2×3 and other 2×n reconstructions. At saturation, almost the entire surface is occupied by the 2×2 reconstruction. At higher Mg coverages, the growth of a silicide occurs both at RT deposition and upon annealing.