Room-temperature growth of Mg on Si(111): stepwise versus continuous deposition

Abstract

Using low-energy electron diffraction and scanning tunnelling microscopy,we studied the formation of Mg silicide and metallic Mg islands on aSi(111)-7 × 7 surface at room temperature as a function of Mg coverage. Wefound that the mechanism by which Mg islands grew on theSi(111)-7 × 7 surface, and the morphology of the islands that formed, depended on whether the Mg depositionwas performed in a stepwise or continuous manner. When Mg was deposited in a stepwisemanner, with 1 h between deposition events, an amorphous Mg silicide overlayer formed on theSi(111)-7 × 7 surface during the initial stage of deposition (up to 2.0 ML Mg coverage), as shown by the observationof δ7 × 7 and 1 × 1 low-energy electron diffraction patterns. Upon further stepwise Mgdeposition, round-shaped Mg islands grew on the amorphous Mg silicidelayer, as shown by scanning tunnelling microscopy and the emergence of a1 × 1 low-energy electron diffraction pattern. If, on the other hand, the Mg was depositedcontinuously in a single step, hexagonal Mg islands formed on the flat Mg silicide layers,and a and 1 × 1 mixed phase was observed. Moreover, using scanning tunnelling spectroscopy, we confirmed thesemiconducting and metallic nature of the Mg silicide layer and hexagonal Mg islands on theSi(111)-7 × 7 surface depending on their Mg coverage, respectively.