Structural, Optical, Electrical, and Nanomechanical Properties of F-Doped Sno2 Fabricated by Ultrasonic Spray Pyrolysis

Abstract

Transparent conductive oxides (TCOs) are in high demand by optoelectronic devices such as light-emitting diodes, phototransistors, touchscreens, solar cells, and low-emissivity windows. Tin-doped indium oxide (ITO) material is the most predominant in the market and is utilised among the various TCO materials. However, the lack of raw materials and the high cost of indium materials have necessitated the exploration of cost-effective TCOs that can serve as viable alternatives without compromising the desired optical and electrical properties. Tin oxide (SnO₂) films emerge as a promising candidate, offering several benefits, including abundant material sources, inexpensiveness, and non-toxicity. It anticipates producing a higher visible transmittance, excellent electrical conductivity, and good mechanical properties compared to ITO. Moreover, SnO₂ can increase its electrical conductivity by introducing representative dopant elements such as Sb, and F. However, structural, optical, and mechanical properties can affect additional dopant elements. Herein, we have demonstrated fluorine-doped tin oxide (FTO) thin films as a function of F dopant concentration by ultrasonic spray pyrolysis. The FTO thin films achieved excellent properties for FTO coatings such as polycrystalline structure, electrical conductivity (ρ = 9.1 × 10^–5 Ω cm), transmittance in the visible region (average visible transmittance up to 85.0%, with peak values of 96.5%) with a wider band gap between 3.80 and 4.28 eV. The increasing elastic modulus and hardness are related to significant grain boundaries, reaching the highest values of 154.5 ± 18.6 and 12.3 ± 3.6 GPa, respectively. The measured interface adhesion between SnO₂/Si substrate is 9.32 J/m².

Graphical Abstract