A synthetic method for preparing double channelling materials, and an operational mechanism for selective p- and...

A new synthetic strategy and associated mechanism have been developed, in which two carrier conduction channels of n- and p-type semiconductors on the surface of one material are automatically and advantageously selected during surface reactivity. The key step is to uniformly channel non-equilibrium metal oxides of CuO_x and SnO_x throughout the sample by applying a flame chemical vapour deposition technique for 5 s. Unlike the original SnO₂ semiconductor and Cu metal, the resulting material possessed intermediate physicochemical properties. It has been demonstrated that an oxidising gas, NO₂, and reducing gas, H₂S, can be alternately adsorbed, which was facilitated by the automatic selection of p- or n-type channels. This solid-solution sensing method utilizing non-equilibrium compositions can be employed in other applications involving semiconducting metal oxide gas sensing, even at low temperatures.