Performance of TiO2 films obtained by cathodic arc deposition as carbon monoxide gas sensor

A. MÁRQUEZ; A. KLEIMAN; D. G. LAMAS

Conferencia; Twefth Int. Cof. on Plasma Surface Engineering; 2010

Titanium dioxide has been widely investigated in the last years due to its outstandingphysical and chemical properties that turned it into an interesting material for severaltechnological applications such as oxidant gas sensors. Anatase, a crystallinemetastable phase of the TiO2 that can be retained in nanocrystalline materials, is ann-type semiconductor characterized by high electron mobility in which the concentrationconduction electron is dependent on the surrounding atmosphere. Thus, anatase filmsas ceramic gas sensors are based on distinct resistance changes in the presences ofgasses. An efficient technique to produce thin films due to its high deposition rate andthe high adherence of the coatings is cathodic arc deposition (CAD). The structure offilms produced by CAD depends significantly on the substrate temperature during thecoating process.In this work TiO2 thin films prepared by CAD on glass and silicon substrates werecharacterized toward its implementation in gas sensors. Thefilms were grown in anoxygen environment (~2 Pa) employing a 100 A continuous arc. They were synthesizedat 400 ºC and at room temperature. The films obtained at 400 ºC grew mainly inanatase phase with the presence of small quantities of rutile phase, while filmssynthesized at room temperature resulted amorphous and were crystallized in anatasephase with a post-annealing at 400 ºC. The crystal structure of the films was studied byx-ray diffraction in the glancing angle geometry, the morphology was observed byatomic force microscopy and reflectance measurements in the visible range were alsoperformed. The film electrical conductivity was investigated at room temperature and inthe temperature range 400~500°C in air and with CO concentrations varying from 20 to200 ppm.Keywords