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

Abstract

Single-layer undoped and 10mol% molybdenum (Mo)-doped vanadium oxide (V2O3) thin films with thicknesses of approximately 342nm 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 253.15K). 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 0.032Ω·cm and 0.071Ω·cm for undoped and Mo-doped vanadium oxide films, respectively, after annealing under 20sccm N2 at 673.15K. Consequently, the equilibrium surface temperature of the single-layer Mo-doped vanadium oxide thin film increases from 253.15K to 299.46K upon induced Joule heating at a current density of 0.1A·cm−2. Thus, it is concluded that single-layer NTC Mo-doped vanadium oxides can be effectively used for cold-start fuel cell applications.