Effect of long-term storage on the electronic structure of semiconducting silicon wafers implanted by rhenium ions

Abstract

Rhenium-doped silicon samples had been synthesized by means of re-pulsed ion implantation (fluences 2.5 × 1017 cm−2, 1 × 1017 cm−2 and 5 × 1016 cm−2) and then stored under natural air-media conditions 5 years. The electronic structure of these samples was studied using combined XPS-and-DFT method. It was confidently established and demonstrated by means of XPS electronic structure mapping (core levels, valence band) that weak acidification occurs. The influence of air media leads to O…Si–O…[Re0] and …Re–Si–O… bonding appearance in the structure of 5-year aged samples rather than to normal rhenium oxidation. No any traces of RexOy sub-oxide fractures were neither found experimentally nor predicted theoretically. DFT-derived acidification scenario points out energetically preferable Re atoms pairing when low concentrations ion-doping regime is applied and metallic Re clusterization in the high concentrations ion-doping regime. Experimentally established essential transformation of initial vicinity states in the top of valence bands by means of Re 5d doping is in a good agreement with DFT calculations of electronic structure and formation energy values of acidification process.