The reaction of Si(001) with magnesium and calcium

We use a novel three-layer model function to assess the effect of the electron donors Mg and Ca on the Si(001) surface. The model shows that the previously unassigned C and D contributions of the Si 2p spectrum are due to the third surface layer. The layer-wise response of the Si(001) surface to the deposition of Mg atoms shows that the essential character of the dimer reconstruction initially remains in place, but is modified in discernible ways by charge donated to the dimer atoms. At larger coverage a new, well-organized silicide structure emerges which is identified as Mg2Si. A study of the reaction with Ca reveals a Ca2Si overlayer at room temperature, but CaSi2 overlayer at high temperature. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3549256]