Molybdenum-doped BiVO₄ thin films deposited through chemical spray pyrolysis for ammonia sensing at room temperature

Highly crystalline pure and Mo-doped (doping at different concentrations) BiVO₄ thin films were deposited on glass substrates using the chemical spray pyrolysis technique. The doping concentration greatly influenced the film's crystallite size and surface roughness. The higher the dopant concentration, the smaller the crystallite size and the higher the surface roughness. All the films were sensitive to ammonia gas. Of all the films tested for gas sensing, the Bi_1-0.05Mo_0.05VO₄ had a higher response to ammonia at room temperature. The introduction of dopant also reduced the bandgap of BiVO₄. Peak shifts in Raman bands were also observed on doping with Mo. The lattice strain and dislocations imposed by the Mo dopant resulted in higher sensor response for the films at room temperature.