Sb incorporated SnO2 nanostructured thin films for CO2 gas sensing and humidity sensing applications

• Pure and antimony doped SnO 2 thin films were fabricated by sol- gel spin coating technique. • The crystallite size was decreased with increasing the Sb doping concentration in SnO 2 . • The optical bandgap energy was varied from 3.65 to 4.03 eV. • Sample C0 shows the highest gas response at the inflection point of 30 °C (ambient temperature). • Sample C0 was found suitable for humidity sensing. Antimony-doped SnO 2 (SnO 2 :Sb) thin films were deposited on glass substrates via sol-gel spin coating and tested for CO 2 gas and humidity sensors. The dominant peak (110) of XRD pattern of SnO 2 :Sb thin films confirmed the cassiterite tetragonal structure regardless of Sb dopant concentration. The spherical particles like morphology were found for all sample and confirmed by scanning electron microscopy (SEM). The transmittance spectra were recorded in the wavelength range 300–800 nm and the optical bandgap was varied from 3.65 to 4.03 eV on increasing Sb concertation in SnO2. From I-V characteristics, sample C3 has the minimum resistivity (1.08 × 10 8 Ω.cm) and maximum conductivity 9.23 × 10 −9 (Ω.cm) −1 at bias voltage 5 V. The gas sensing characteristics of Sb-SnO 2 thin films were examined at different operating temperatures (30 °C to 80 °C) for sample C0 to C4. The optimized sample C0 have gas sensor response 78.5% at ambient temperature (30 °C). The higher doping of Sb in SnO 2 as sample C3 and C4 were suitable for higher operating temperatures (80 °C) and responses were 18.74% and 71%, respectively. The characteristics of humidity sensors were analysed in relative humidity (%RH) range from 10% to 90%RH for Sb-SnO 2 thin films and found suitable for sample C0 at ambient temperature in mid humidity range (35–60%RH). The present study is an attempt to design a cost-effective and low-temperature-based resistive CO 2 gas sensor and humidity sensor for the enhancement in sensing properties.