Highly a-axis-oriented nanostructured thin films of 0.5 atom % Ba-doped In2O3 exhibited high sensitivity toward 3 ppm (threshold limit values of NO2) of NOx, consistently and reproducibly. Thin films prepared by pulsed laser (KrF, lambda = 248 nm) deposition are highly granular, exhibiting wirelike geometry with an average diameter of similar to 80 to 100 nm. Sensing mechanism as investigated by X-ray photoemission studies reveals that adsorption of NOx on the surface of the film acts as a trap for conduction electrons due to its high electron affinity, which provides a different chemical environment for the surface indium ions. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3485037] All rights reserved.