Synthesis, characterization, and transport properties of single-layer pure and molybdenum-doped vanadium oxide thin films on metallic conductive substrates

Single-layer undoped and 10 mol% molybdenum (Mo)-doped vanadium oxide (V₂O₃) thin films with thicknesses of approximately 342 nm are fabricated by an aqueous sol–gel method and then deposited onto 316L stainless steel conductive substrates. The influence of various annealing temperatures (in a nitrogen atmosphere) on the structural and electrical properties of undoped and Mo-doped vanadium oxide thin films is investigated. Through a controlled annealing process, the electrical resistances of the single-layer thin films are optimized to attain the required amount of Joule heating for cold-start fuel cell applications within an ambient temperature range (273.15 to 253.15 K). The films show a negative temperature coefficient (NTC) behavior and a transition from a metal to an insulator at sub-zero temperatures. The highest electrical resistivities are measured to be 0.032 Ω·cm and 0.071 Ω·cm for undoped and Mo-doped vanadium oxide films, respectively, after annealing under 20 sccm N₂ at 673.15 K. Consequently, the equilibrium surface temperature of the single-layer Mo-doped vanadium oxide thin film increases from 253.15 K to 299.46 K upon induced Joule heating at a current density of 0.1 A·cm⁻². Thus, it is concluded that single-layer NTC Mo-doped vanadium oxides can be effectively used for cold-start fuel cell applications. - Highlights: • Single-layer undoped and 10 mol% Mo-doped vanadium oxide films were fabricated. • Mo-doped V₂O₃ thin films showed am enhanced NTC behavior through annealing. • Mo-doped V₂O₃ thin films revealed the high resistivity of 0.071 Ω·cm at 253.15 K. • Remarkable temperature rise of a Mo-doped V₂O₃ film was achieved by Joule heating. • Mo-doped V₂O₃ films can be effectively used for cold-start fuel cell applications.