Tunneling through surface barrier and oxygen in-diffusion in nanostructured SnO2 gas sensors

The surface barrier of SnO2 was modeled for grains with average radius, R, larger than the depletion width, w, and of the same size, respectively. The model allowed us to explain the different behavior of conductance in gases of two sets of sensors with grains having well distinct characteristic radii, e.g., R=60nm, and R=150nm. In the first case (R=60nm), the barriers touch at the centre of the grain, an effect which strongly modifies the transport properties. The electrical behavior has been explained through the mechanism of barrier modulation through gas chemisorptions and oxygen in-diffusion, taking into account of tunneling contribution. © 2011 American Institute of Physics.