A simple chemical reduction approach to dope β-FeSi2 with boron and its comprehensive characterization

Abstract

β-FeSi₂ has been doped with Boron via a novel and cost-effective chemical reduction of the glassy phase of [(Fe₂O₃ + 4SiO₂ + B₂O₃ + FeBO₃ + Fe₂SiO₄)] using Mg metal at 800 °C. Doped β-FeSi₂ has been investigated via extensive characterization and detailed analysis using first-principles calculations. The reduction in the d-spacing as can be observed from the XRD peak shift as well as the blue shift of the β-Raman line along with the right shift of Si and Fe 2p peaks indicate the B doping. The Hall investigation basically demonstrates p-type conductivity. Hall parameters were also analyzed using thermal mobility and dual-band model. The temperature profile of R_H demonstrates the contribution of shallow acceptor levels at low temperatures, whereas the deep acceptor level contributes at high temperatures. Dual-band investigation reveals a substantial increase in the Hall concentration with B doping due to the cumulative contribution of both deep and shallow acceptor levels. The low-temperature mobility profile exhibits phonon and ionized impurity scattering just above and below 75 K, respectively. Moreover, it demonstrates that holes in low-doped samples can be transported more easily than at higher B doping. From density functional theory (DFT) calculations, the origin of the dual-band model has been validated from the electronic structure of β-FeSi₂. Further, the effects of Si and Fe vacancies and B doping on the electronic structure of β-FeSi₂ have also been demonstrated. The charge transfer to the system due to B doping has indicated that an increase in doping leads to higher p-type characteristics.