Fig. 6: Schematic showing the mechanism behind the formation of NN, PP, and PN junctions in SnOx-CuOx solid-solution samples following FCVD.

a NN and PP junctions formed in three dimensions. b Types of channels formed at the electrodes and the direction of mobile carriers. c Changes in NN channel, PN junction, and resistance when NO2 gas is adsorbed. d Changes in PP channel and resistance when H2S gas is adsorbed