Local geometry around B atoms in B/Si(1 1 1) from polarized x-ray absorption spectroscopy

Abstract

The arrangement of B atoms in a doped Si(111)-( √ 3 × √ 3)R30 • :B system was studied using 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 c 1 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 c 1 -atoms is at the surface, next to those Si atoms which form the ( √ 3× √ 3)R30 • reconstruction.