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Semiconductor thin film sensor based on γ-Fe2O3 for CH4 detection

Dzmitry A. Kotsikau 1Maria I. Ivanovskaya 1Simonetta Capone 2Pietro Siciliano 2Luca Francioso 2

1. Institute for physical chemical problems of the Belarusian State University, Minsk, Belarus
2. Institute of Microelectronics and Microsystems (IMM-CNR), Lecce, Italy


Generally, thin film sensors based on semiconductor oxides (In2O3, SnO2, Fe2O3) are characterised by improved performance when detecting gases of acceptor nature (NOx, O3) and C2H5OH. Sensitivity of thin films to reducing gases is extremely low. In order to improve the characteristics of thin films to flammable gases, oxide layers are commonly been doped with noble metals. It is essentially, that gas-sensitive features of Fe2O3 are strongly determined by its structural features like phase composition, dispersity, defectiveness, morphology etc. γ-Fe2O3 is used as an individual layer and as a component of a multi-layer structure of ceramic sensors for detection of flammable gases. In the present work we report a study of gas-sensitive behaviour of γ-Fe2O3 thin films deposited on Si-substrate. The sensitive layers were formed from the stabilised sol of Fe2O3 prepared by the sol-gel rout. The sol was deposited onto micromachined Si-substrates of new design. Structure of the material was studied by XRD, HR-TEM, DTA/TG, FT-IR and Mössbauer spectroscopy. The applied conditions of Fe2O3 synthesis allow to obtain thin-film γ-Fe2O3, which is metastable at r.t. As it follows from the DTA/TG data, thus prepared γ-Fe2O3 remains stable up to 485 C. TEM characterisation gives spherical particles of size as high as 3-9 nm. Non-uniformity of the grain size distribution provides good quality of the films and close contact between grains. Thin film sensor, based on highly dispersive γ-Fe2O3, is characterised by high sensitivity to CH4. Suitable sensitivity of the sensor to 100 ppm of CH4 is reached at 350-425 C. Besides, the dynamic response profiles are well reproducible under repeated exposition of CH4. Optimal operating temperature, at which the sample shows maximum response, fastest dynamics and linear response vs. concentration dependence, is found to be 425 C. This work was supported by the GASMOH project (2000-10041).


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Presentation: poster at E-MRS Fall Meeting 2004, Symposium A, by Dzmitry A. Kotsikau
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-05-19 12:05
Revised:   2009-06-08 12:55