Abnormal p-type to n-type switching during nitric oxide gas sensing: Ni(OH)2 nanoplatelets on amorphous NiO seed layers. (June 2022)

• Record Type: Journal Article
• Authors: Nkosi, Steven S.; Mkwae, Prince S.; Ogundipe, Sunday A.; Leshabane, Nompumelelo; Revaprasadu, Neerish; Kroon, R.E.
• Is Part Of: Vacuum. Volume 200(2022)
• Publication Date: 2022-06
• Subjects: NiO -- NiO/Ni(OH)2 -- p-type to n-type transition -- NO gas Sensor; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2022.111032
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: NiO films were deposited on corning glass by DC magnetron sputtering at different substrate temperatures up to 450 °C and found to generally be amorphous. Gas sensing measurements were performed at room temperature in the presence of relative humidity of 10%. The NiO film produced with 350 °C substrate temperature showed a p-type conductivity response when exposed to NO gas with high response of 12 at 5 ppm. The response of the films was also tested with ammonia and hydrogen interfering gases. The NiO films were further used as seed layers to grow Ni(OH)2 nanoplatelets hydrothermally. The Ni(OH)2 nanostructures grown on NiO (otherwise referred to as NiO/Ni(OH)2 nanostructures) at substrate temperature of 100 °C or room temperature showed an n-type conductivity behaviour towards different concentrations of NO gas. However, the NiO/Ni(OH)2 nanostructures prepared at substrate temperatures of 200 and 350 °C showed a p-type conductivity at lower concentrations (below 80 ppm) and switched to n-type behaviour at higher concentrations (80 ppm and above). An abnormal irreversible transition from p-type to n-type conductivity triggered by an increase in nitric oxide (NO) gas concentration is reported for Ni(OH)2 nanoplatelets on amorphous NiO films at room temperature. Highlights: Synthesis of poorly crystalline with amorphous phases of NiO seed and NiO/Ni(OH)2 . Room Temperature NOx highly sensitive and selective gas sensing. Room Temperature Abnormal p-n transition of amorphous NiO/Ni(OH)2 . p-type NiO seed layer and n-type NiO/Ni(OH)2 NO gas sensing.