XPS analysis of bridging and non-bridging oxygen in Yb³⁺-Er³⁺-Tm³⁺-doped zinc-tellurite glasses

Influence of Er³⁺, Yb³⁺ and Tm³⁺ on the network structure of zinc-tellurite glasses is investigated by refraction index and high-resolution X-ray photoelectron spectroscopy (XPS) in order to clarify the role of rare-earth ions in the formation of non-bridging and bridging oxygens (NBO and BO, respectively). The NBO atoms were responsible for high polarizability, as confirmed from the correlations between the local structure and polarizability, where have been tentatively established high linear fit r²=0.96 and 0.98 when the excitation wavelengths are 532 and 632.8 nm, respectively. The structural origin of the NBO atoms into the zinc-tellurites glasses is discussed by analysis of the component number from the deconvolution in the XPS spectra. In this analysis, Te 3d peaks shift by about 0.23 eV towards higher binding energy from TZ1 to TZ4, and spin-orbit splitting between Te 3d_5/2 and Te 3d_3/2 to all glasses remain unchanged, ΔE ≈10.4 eV. While Zn 2p peaks shift by about 1.08, eV towards higher binding energy, and spin-orbit splitting between Zn 2p_3/2 and Zn 2p_1/2 increase of 23.08 eV (TZ1 to TZ3) to 24.09 eV (TZ4) whit the increase REI. The O 1s spectra suggest that the increase of REI concentration produces additional environments for REI with bonds through lone-pair electrons, favoring the formation of NBOs. It was observed that the increasing the concentrations of REI has a high linear dependence with increased of NBO atoms in the glass network, r²=0.87.