Applied chemistryApplied chemistry Z 0300 Solid State Gas Sensors: State of the Art and Future Activities -[67 refs.]. -(CAPONE, S.; FORLEO, A.; FRANCIOSO, L.; RELLA, R.; SICILIANO, P.; SPADAVECCHIA, J.; PRESICCE, D. S.; TAURINO, A. M.; J. Optoelectron. Adv. Mater. 5 (2003) 5, 1335-1348; Ist. Microelettron. Microsistemi, Sez. Lecce, I-73100 Lecce, Italy; Eng.) -Schramke 29-283

No abstract

We report the fabrication of libraries of nanostructured TiO2 films with a gradient in nanoparticle crystalline phase and dimensions. By supersonic cluster beam deposition it is possible to produce rutile nanoparticles with a diameter smaller than 10nm and to spread them into a co-deposited amorphous titania matrix. Upon thermal annealing rutile nanocrystals act as growth seeds of a film with a spatially controlled rutile/anatase ratio. Films with controlled crystalline phase variation have been deposited on micropatterned substrate to produce arrays of chemoresistive sensors of volatile organic compounds. Devices with different nanocrystalline structures and performances are obtained by a simple one-step thermal treatment after deposition.

Gas sensors have been prepared by using single crystalline MoO3 nanorods. Structures 50–150nm and up to 15μm in length were synthesized by template directed hydrothermal synthesis. Gas sensing tests showed responses to NO2 up to 740% and to NH3 up to 570%. Moreover, preliminary electrical characterizations were performed, as a function of temperature in 20–520°C range temperature, by means of current-voltage measurements. I-V dependence studies show a linear increase in current at low voltage and a quadratic increase at higher voltages. A study of the current-temperature dependence shows that at high temperature current is thermally active and successively decreases that can be explained by taking in account a change of material morphology.

No abstract