Structure determination of the Si3N4/Si(111)-(8 x 8) surface: A combined study of Kikuchi electron holography, scanning tunneling microscopy, and ab initio calculations

A comprehensive atomic model for the reconstructed surface of Si3N4 thin la yer grown on Si(lll) is presented. Kikuchi electron holography images clear ly show the existence of adatoms on the Si3N4(0001)/Si(111)-(8 x 8) surface . Compared with the nb initio calculations, more than 30 symmetry-inequival ent atomic pairs in the outmost layers are successfully identified. Scannin g tunneling microscopy (STM) images show diamond-shaped unit cells and nine adatoms in each cell. High-resolution STM images reveal extra features and are in good agreement with the partial charge density distribution obtaine d from total-energy calculations.