Structural stability and electronic properties of alkaline-earth metals (Ca, Sr, Ba) induced Si(111)-3x2 surfaces have been comprehensively studied by means of ab initio calculations. Adsorption energy and charge density difference calculations show the high structural stability due to the strong chemical bonding. Analysis of electronic band structures and band-decomposed charge density distributions indicates that the third valence band is deriving from top Si and metal atoms, while the top most two valence bands are deriving from the bulk silicon. These results suggest a larger surface band gap of 1.65-1.68 eV, which is good consistent with the recent experimental finding for Sr/Si(111)-3x2 surface. These results reveal a natural explanation for the relevant experimental observation and stimulate further experimental and theoretical exploration on the surface science.
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