Structural, electrical and gas-sensitive properties of Cr2O3 thin films

Cr2O3 thin films were synthesized by RF magnetron sputtering of a Cr target in an oxygen-argon plasma. The effect of annealing temperature on the structural, electrical, and gas-sensitive properties of the Cr2O3 thin films was studied. According to AFM, SEM, XRD, EDX, XPS, optical spectroscopy and electrical measurements the annealed films were characterized by a polycrystalline structure, high stoichiometry, p-type conductivity and a band gap energy of 3.3 ± 0.2 eV. An increase in the annealing temperature from 350 to 450 °C leads to formation of Cr2O3 grains with a diameter from 30 to 130 nm and to a significant increase in the film electrical resistance. Cr2O3 demonstrated sensitivity to NO2, H2, NH3, vapors of acetone and toluene in the heating temperature range of 25–200 °C. Changing the annealing temperature allows to control the sensitivity of the films to certain gases. Thus, Cr2O3 thin films subjected to annealing at a temperature of 450 °C were characterized by a high response to NH3, while those annealed at a temperature of 400 °C – to toluene vapors and that annealed at 350 °C – to NO2 and acetone vapors. A qualitative model of the sensory effect was proposed.