Improving the properties of FeO by a sparking method under a uniform magnetic field for a high-performance humidity sensor.

Iron oxide (FeO) thin films are promising semiconductors for electronic applications because FeO is an earth-abundant semiconductor with an appropriate band gap. However, many methods for the synthesis of FeO thin films require a corrosive source, complex procedures, and many types of equipment. Here, we report, for the first time, a simple method for FeO deposition using sparking under a uniform magnetic field. The morphology of FeO displayed an agglomeration of particles with a network-like structure. The crystallite size, % Fe content, and optical bandgap of FeO were influenced by changes in the magnitude of the magnetic field. For application in humidity sensors, FeO at a magnetic field of 200 mT demonstrated a sensitivity of 99.81%, response time of 0.33 s, and recovery time of 2.57 s. These results can provide references for new research studies.