RF sputtered SnO2: NiO thin films as sub-ppm H2S sensor operable at room temperature.

A room temperature sub-ppm H 2 S sensor based on RF sputtered SnO 2 : NiO thin film has been demonstrated. For this, SnO 2 thin films have been modified with ultrathin layers (30 nm) of NiO. These films were characterized using Scanning electron Microsopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Gas sensing properties of these films were systematically investigated and compared with those of pure SnO 2 and NiO films. Sensing studies revealed that these films are highly sensitive to H 2 S at room temperature. The sensor response exhibited by NiO modified SnO 2 film, is 9 and 415 times greater than that exhibited by pure SnO 2 and NiO films, respectively. The sensor response in case of SnO 2 :NiO is due to contribution from two different mechanisms- (i) oxidation reaction between adsorbed oxygen and H 2 S and (ii) destruction of p-n junctions due to conversion of Nickel Oxide to metallic Nickel Sulphide (product of chemical reaction between NiO and H 2 S). Presence of XPS sulphide peaks at binding energies of ∼163 eV corresponding to S-2p 3/2 and S-2p 1/2 , on H 2 S exposure confirms the formation of Nickel Sulphide. Present experiments proved the ability of these films to detect low concentrations of H 2 S i.e. parts per billion reproducibly. These films were also found to be stable for extended period of time, hinting at commercial viability of the sensor. [ABSTRACT FROM AUTHOR]