Abstrakt
The arrangement of B atoms in a doped Si(111)-(root 3x root 3)R30 degrees:B system was studied using a near-edge x-ray absorption fine structure (NEXAFS). Boron atoms were deposited via segregation from the bulk by flashing the sample repeatedly.
The positions of B atoms are determined by comparing measured polarized (angle-dependent) NEXAFS spectra with spectra calculated for various structural models based on ab initio total energy calculations. It is found that most of boron atoms are located in sub-surface L positions, beneath a Si atom.
However, depending on the preparation method a significant portion of B atoms may be located elsewhere. A possible location of these non-L-atoms is at the surface, next to those Si atoms which form the (root 3x root 3)R30 degrees reconstruction.