Room-temperature NH3 gas-sensing characteristics of spray-deposited transition metal ions substituted CoFe2O4 thin films

We report here the structural, morphological and gas-sensing characteristics of 1, 3 and 5 wt. % Cr3+- and Zn2+-substituted CoFe2O4 thin films prepared using the facile solution-based spray pyrolysis experimental method. Structural study confirms the polycrystalline nature and single-phase cubic spinel structure of the deposited films. Atomic force microscopy (AFM) study demonstrates that the substitution of transition metal ions significantly influences the surface topography of pristine CoFe2O4 thin films. Results from the gas sensor analysis reveal an excellent sensing behavior of Cr3+-substituted CoFe2O4 at room temperature, in particular, the maximum gas response is observed for 1 wt. % Cr3+-substituted CoFe2O4 thin films than that of pristine and other substituted CoFe2O4 thin films, which is due to the substitution of Fe3+ by Cr3+ provides more reactive sites, at this particular concentration, and thus relatively higher response. In addition, the selectivity, gas response, response time and recovery time of CoFe2O4 thin films have been explored in the present study, and the deposited thin films show high selectivity for NH3 gas than that of other tested toxic gases. Hence, based on the results obtained, spray-deposited Cr3+-substituted CoFe2O4 thin films would act as potential candidates for the fabrication of NH3 sensor devices even for detecting low ppm gas concentrations at room temperature.

Automated summary

This study reports the characteristics of Cr3+- and Zn2+-substituted CoFe2O4 thin films prepared by solution-based spray pyrolysis method. The results show that the substitution of transition metal ions significantly affects the surface topography and gas-sensing behavior of the films. Cr3+-substituted CoFe2O4 thin films exhibit excellent sensing behavior towards NH3 gas at room temperature.