New gas sensitive MIS structures Pt/Al2O3(M = Pt, Rh)/Si with a granular dielectric layer

New gas sensitive MIS structures Pt/Al2O3(M)/p-Si, where M = Pt, Rh, with granular dielectric Al2O3 layers doped with noble metals were obtained by an aerosol pyrolysis method. Surface morphology and composition of the structures were studied by TEM, AFM and EPMA. Sensor properties of the MIS structures were studied towards reducing gases (1000 ppm H2, 300 ppm CO, 1000 ppm CH4 in air) at 100 and 200 °C. The Pt/Al2O3(M = Pt, Rh)/Si structures showed a very high sensor response to reducing gases. A shift of C–V characteristics was up to 2.5 V under CO, 2.2 V under hydrogen and 0.7 V under methane. High values of shift of C–V curves can be related with cooperative influence of a change of surface state density in dielectric layer, reduction of platinum electrode and dipole layer formation.