Our study of the fundamental principle of gas sensing and its improvement by doping is based on single-crystalline In2O3 films (without grains) as simple model systems. In these films only two electrically parallel conductance contributions, bulk and surface (Fig. 2b), add up to the measured conductance. Systematically disabling the bulk or surface conduction by controlled bulk doping with the deep acceptor Mg or by oxygen-plasma surface treatments, respectively, allowed us to show that the gas response on oxidizing gases (Fig. 3) is fundamentally based on the modulation of the surface conductance whereas the bulk conductance remains unaffected. With these results we could rationalize the increased gas sensitivity after bulk Mg-doping (Fig. 3) by disabling the gas-insensitive parallel bulk conductance. Our concept of using the surface conduction for gas sensing and removing the bulk conductance (or intra-grain conductance in poly-crystalline material) by deep acceptor doping can be generally applied to other n-type oxides, such as the widely-used gas-sensor material tin dioxide (SnO2).
|1||Author||J. Rombach , A. Papadogianni , M. Mischo , V. Cimalla , L. Kirste , O. Ambacher , T. Berthold , S. Krischok , M. Himmerlich , Sören Selve , O. Bierwagen|
The role of surface electron accumulation and bulk doping for gas-sensing explored with single-crystalline In2O3 thin films
|Source||Sens. Actuators B Chem. , 236 , 909 ( 2016 )|
: 10.1016/j.snb.2016.03.079 |