X-ray photoelectron spectroscopy analysis of boron defects in silicon crystal: A first-principles study

We carried out a comprehensive study on the B 1s core-level X-ray photoelectron spectroscopy (XPS) binding energies and formation energies for boron defects in crystalline silicon by first-principles calculation with careful evaluation of the local potential boundary condition for the model system using the supercell corresponding to 1000 Si atoms. It is reconfirmed that the cubo-octahedral B₁₂ cluster in silicon crystal is unstable and exists at the saddle point decaying to the icosahedral and S₄ B₁₂ clusters. The electrically active clusters without any postannealing of ion-implanted Si are identified as icosahedral B₁₂ clusters. The experimentally proposed threefold coordinated B is also identified as a 〈 001 〉 B - Si defect. For an as-doped sample prepared by plasma doping, the calculated XPS spectra for complexes consisting of vacancies and substitutional B atoms are consistent with the experimental spectra. It is proposed that, assuming that the XPS peak at 187.1 eV is due to substitutional B (B_s), the experimental XPS peaks at 187.9 and 186.7 eV correspond to interstitial B at the H-site and 〈 001 〉 B - Si defects, respectively. In the annealed samples, the complex of B_s and interstitial Si near the T-site is proposed as a candidate for the experimental XPS peak at 188.3 eV.