Figure 5.

Reaction of pre-chemisorbed oxygen and sensing mechanism of p-type CaFe₂O₄ nanoparticles based on density of charge in the core shell and energy band diagram (a) dark condition (b) photo-activation (i.e., light is ON) (c) condition prior to any surface reaction (d) trapping electron from the valence band due to the pre-chemisorption process in dark condition results in the formation of a hole-accumulation layer (HAL) (e) photo-activation process increases the density of majority charge (hole) resulting in a widening of HAL.