THE EFFECT OF SB DOPING ON CRYSTAL STRUCTURE AND THE Sn4⁺ → Sb5⁺ SUBSTITUTION MODEL WITH OXYGEN DEFECT FORMATION

Background. Transparent conducting oxides (TCOs) are key functional materials for modern optoelectronic devices, including touch screens, solar cells, and light-emitting diodes. Antimony-doped tin dioxide (SnO₂:Sb) is of particular interest as an alternative to the more expensive indium tin oxide (ITO) due to its high thermal and chemical stability, as well as the availability of raw materials. However, the mechanisms of Sb incorporation into the SnO₂ crystal lattice and its influence on electrical and optical properties remain insufficiently studied. The objective of this research is a theoretical and experimental investigation of the substitution processes of tin atoms with antimony atoms in different oxidation states (Sb³⁺ and Sb⁵⁺) and the determination of optimal synthesis conditions for producing TCOs with improved characteristics. Materials and methods. Thin SnO₂:Sb films were deposited using spray pyrolysis from precursor solutions of SnCl₄·5H₂O and SbCl₃ in a mixture of ethanol and deionized water at a substrate temperature of 450 °C. The antimony concentration was varied from 0 to 10 at. %. To improve crystallinity and activate dopants, the samples were thermally annealed at 600 °C for 1 hour. The structural, electrical, and optical properties of the films were studied using a comprehensive set of advanced techniques, including surface resistance, charge carrier mobility and concentration, as well as transmission, refraction, and absorption coefficients. Results. It was found that at an optimal antimony concentration (3–5 at. %) and properly selected synthesis conditions, Sn⁴⁺ is predominantly substituted by Sb⁵⁺, leading to donor doping and a significant improvement in conductivity while maintaining high transparency in the visible range (80–90 %). At Sb concentrations above 5 at. %, the formation of compensating defects and phase segregation was observed, resulting in degraded electrical properties. Thermal annealing enhanced crystallinity, reduced defect concentration, and activated Sb dopants, leading to a decrease in resistivity from 10⁻²–10⁻³ Ω·cm to 10⁻³–10⁻⁴ Ω·cm. Conclusion. This study established fundamental mechanisms of antimony incorporation into the SnO₂ crystal lattice and optimized spray pyrolysis synthesis parameters for producing high-quality SnO₂:Sb-based TCOs. The developed material exhibits a combination of high transparency, good conductivity, and thermal stability, making it promising for various optoelectronic applications, including solar cells and touch screens. The use of cost-effective and environmentally friendly materials promotes sustainable technological development and reduces reliance on rare and expensive elements.