Room Temperature Visible Light Activated p-type Semiconductor Gas Sensors Based on CaFe2O4 Nanopowders

Gas sensors based on CaFe2O4 nanopowders, which are p-type metal oxide semiconductor (MOX), have been fabricated and assessed for ethanol gas monitoring under visible light activation at room temperature. Regardless of their inferior sensitivity compared to thermally activated counterparts, the developed sensors have shown responsive sensing behavior towards ethanol vapors confirming the ability to use visible light for sensor activation. LEDs with different wavelengths (i.e., 465–590 nm) were employed. The highest sensitivity (3.7%) was reached using a green LED activation that corresponds to the bandgap of CaFe2O4.