Centers of near-IR luminescence in Bi-doped SiO2 and GeO2: First-principle modeling and experimental data analysis

TL;DR

This study combines first-principle modeling and experimental data analysis to identify the bismuth-related centers responsible for near-IR luminescence in SiO2 and GeO2 glasses, revealing specific complexes and substitutional centers as key contributors.

Contribution

It provides the first comprehensive theoretical and experimental comparison to identify the specific bismuth centers responsible for IR and visible luminescence in these glasses.

Findings

IR luminescence is likely caused by Bi...Si-Si and Bi...Ge-Ge complexes.

Red luminescence in SiO2:Bi is probably due to divalent Bi substitutional centers.

Theoretical spectral properties match experimental data for identified centers.

Abstract

First-principle study of possible bismuth-related centers in SiO2 and GeO2 hosts is performed and the results are compared with the experimental data. The following centers are modeled: trivalent and divalent Bi substitutional centers; BiO interstitial molecule; interstitial ion, Bi^+, and atom, Bi^0; Bi...Si-Si and Bi...Ge-Ge complexes formed by interstitial Bi atoms and glass intrinsic defects, Si-Si or Ge-Ge oxygen vacancies; interstitial dimers, Bi0 and Bi_2^-. Experimental data available on bismuth-related IR luminescence in SiO2:Bi and GeO2:Bi glasses, visible (red) luminescence in SiO2:Bi glass and the luminescence excitation are analyzed. Comparison of the calculated spectral properties of the bismuth-related centers with the experimental data shows that IR luminescence in SiO2:Bi and GeO2:Bi is most likely caused by Bi...Si-Si and Bi...Ge-Ge complexes and divalent Bi substitutional center is probably responsible for the red luminescence in SiO2:Bi.