NON-THERMAL PLASMA EFFECT OF LI DOPED NIO THIN FILMS PREPARED BY THE SPRAY PYROLYSIS TECHNIQUE FOR SENSOR APPLICATIONS
In, this research, pure nickel oxide NiO and Lithium-nickel oxide NiO:Li films were prepared on to glass substrates at a temperature of 450°C, by using the spray pyrolysis technique to develop the gas sensor, utilizing nickel and lithium chlorides as precursors. The effect of non-thermal plasma at (3,5,7sec) on the structural, optical, and electrical properties for NiO:Li thin films were studied. XRD pattern shows all films are polycrystalline belonging to cubic structure and the intensity was around the plane of (111).In addition, using SEM images, all samples exhibit porous with nanoparticles in the range (16-33nm ) as size. Optical measurements revealed that pure NiO and NiO:Li films have direct energy gaps (Eg) and decrease (from 3.65eV to 3.60eV), respectively. The optical energy gap was reduced after exposure to non-thermal plasma for 3,5,7 seconds (3.50, 3.45, 3.30eV) respectively. The results of Hall effect showed that the electrical conductivity of all films were of the p-type. The gas sensing performance of the prepared films towards NO2 gas was studied at various working temperatures, including (RT, 100 oC, 200 oC, and 300 oC). The current study found that pure NiO and NiO:Li films deposited can detect nitrogen dioxide gas at low work temperatures, where showed pure NiO, NiO:Li films sensitivity towards nitrogen dioxide NO2 gas at an operating temperature RT about 26.1% , 36.8% respectively. After exposure to non-thermal plasma at (3,5,7sec), the sensor NiO:Li showed an increase in sensitivity, and the best sensitivity was towards NO2 gas at room temperature for the sample exposed to non-thermal plasma at (7 sec) (49.9 percent ). The same sample showed a maximum sensitivity towards NO2 gas at 200 oC about (80.2%) with moderate response and recovery time. The influence of non-thermal plasma leads to good sensing performance for NiO:Li films, as shown in the study.
Keywords: Non-Thermal Plasma; Nio Doped Li; XRD; Spray Pyrolysis Technique, NO2 Gas.