Multilayered metal oxide thin film gas sensors obtained by conventional and RF plasma-assisted laser ablation

Reactive pulsed laser ablation has been established as a feasible method for thin film deposition of a large variety of compounds with simple or complex stoichiometry such as oxides, nitrides, semiconductors and superconductors. This technique relies on photoablation of pure elements, or a mixture of materials, with simultaneous exposure to a reactive atmosphere. The reactivity of the plasma plume can be enhanced if the ambient gas is excited, for example by an additional RF discharge. In the case of oxides, reactions between the laser vaporized metals and oxygen lead to the formation of intermediate complexes and finally to oxide thin films. SnO2-based multilayered thin films of In2O3, have been deposited by conventional and RF plasma-assisted Reactive Pulsed Laser Ablation, with the aim to evaluate their behaviour as toxic gas sensors. The depositions have been carried out by a frequency doubled Nd-YAG laser (? = 532 nm, ? = 7 ns) on Si(100) substrates, in O2 atmosphere. The thin films have been characterized by X-Ray Diffraction and Electrical Resistance measurements. A comparison of the electrical response of the simple (indium oxide, tin oxide) and multilayered oxides to toxic gas (nitric oxide) has been performed. The influence on the structural and electrical properties of the deposition parameters, such as substrate temperature and RF power, is reported.