TEM investigation of sputtered indium oxide layers on silicon substrate for gas sensors

Abstract

Indium oxide (In2O3) has recently attracted much interest as a material for transparent electrodes in electronic devices such as liquid crystal displays [1], solar cells [2], as a barrier layer in tunnel junctions [3], as sensing material in gas sensors e.g. for ozone [4] and in nanowire technology [5]. Two crystal structures have been reported for In2O3: body-centered cubic (bcc, Ia3, a = 1.0118 nm) and rhombohedral (rh, R-3c, a = 0.5478 nm and c = 1.451 nm) [6]. In the case of bcc-In2O3, the physical and optical properties are well known [1–4], whereas for rh-In2O3, to the best of our knowledge, no information is available. Common deposition methods of In2O3 films and nanostructured layers are evaporation [7], magnetron sputtering [8] and Sol-Gel [9] processing. These deposition processes usually lead to the growth of In2O3 with a poly- or single crystalline bcc structure independent of the used substrate [10].