Local geometry around B atoms in B/Si(111) from polarized x-ray absorption spectroscopy

TL;DR

This study uses polarized x-ray absorption spectroscopy to determine the local geometry of boron atoms in a doped silicon surface, revealing their subsurface and surface positions depending on preparation methods.

Contribution

It provides detailed insights into the atomic positions of boron in doped silicon using polarized NEXAFS and ab-initio calculations, highlighting the variability based on preparation.

Findings

Most B atoms are in subsurface L$_{1}^{c}$ positions beneath Si atoms.

Some B atoms are located at the surface near Si atoms.

Preparation method influences B atom locations.

Abstract

The arrangement of B~atoms in a doped Si(111)-$(\sqrt{3}\times\sqrt{3})R30^{\circ}$: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$_{1}^{c}$ 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$_{1}^{c}$-atoms is at the surface, next to those Si atoms which form the $(\sqrt{3}\times\sqrt{3})R30^{\circ}$ reconstruction.