Temperature dependent donor–acceptor transition of ZnO thin film gas sensor during butane detection

For ZnO thin films excellent hydrogen, carbon monoxide, methane, and butane gas sensing characteristics are reported. First Fourier transformation of the conductance transients together with principal component analyses is found to be very effective in differentiating these combustible gases. At sensor operating temperature in the range 350–380 °C, ‘n’ to ‘p’ type carrier reversal in ZnO thin films were observed only during butane sensing. The mechanism, based on the cracking of alkanes (due to the catalytic activity of ZnO), and reaction of the lattice oxygen of ZnO with the highly reactive species (formed after cracking), explained satisfactorily the observed carrier reversal.