Structural evolution of SnO2TiO2 nanocrystalline films for gas sensors

Abstract

Thin films (50-200 nm) of SnO 2 TiO 2 were deposited on SiO 2 /(001)Si substrates by RF-sputtering and by molecular beam before they were annealed in vacuum at 200-900°C. In-situ TEM, XRD, SEM, Raman and IR-spectroscopy were used to analyze the structure transformations in the SnO 2 TiO 2 films. In the as-deposited state, the films are amorphous. They crystallize at higher temperatures (starting at about 500°C) forming nanosized grains. The problem of the spinodal decomposition in the SnO 2 TiO 2 system observed earlier at high temperatures is discussed also for low-temperature processing. The stoichiometry of the films of both groups (reactive ion sputtered and high-vacuum e-gun sputtered) is being compared.

Gas Semiconducting Sensors Based on Metal Oxide Nanocomposites

“…The second category includes mixed oxides, which form solid solutions. An example of such a system is the mixture of TiO 2 and SnO 2 , which form solid solutions over the entire range of compositions but only above a certain critical temperature (Edelman, et al, 2000;Arakawa, et al, 1997). The third group consists of systems that give neither individual compounds nor solid solutions.…”

“…In this case, initially formed amorphous system containing a mixture of titanium and tin ions (Edelman, et al, 2000) transforms into a nanocrystalline composite upon further annealing. When spraying a mixture of Sn and In salt solutions on the surface of the heated substrate by aerosol method, the synchronous joint growth of crystals of SnO 2 and In 2 O 3 with different crystal lattices produces the composite film, in which the size and state, and in particular, crystal defects strongly depend on the composition of the film and the spraying conditions.…”

Electronic and structural properties of SnxTi1−xO2 solid solutions: a periodic DFT study

“…The knowledge of the bulk electronic structure of this mixed oxide would aid in the design of gas sensing devices and catalysts exhibiting unique features. Therefore, the structural and electronic properties of Sn x Ti 1−x O 2 solid solutions have been subjected to extensive experimental [1,[3][4][5][6]8,[12][13][14][15][16][17][18][19] and recent theoretical [20] studies. A detailed understanding of the electronic structure of Sn x Ti 1−x O 2 solid solution, however, lags behind these achievements.…”

Nanostructured TiO2-based mixed metal oxides prepared using microemulsions for carbon monoxide detection

“…Thus, the larger the atomic ratio of Sn to Ti, the larger the observed dspacing. This shift indicated the formation of a solid solution between TiO 2 and SnO 2 [20,21,39]. The formation of both anatase phase and solid solution can be explained, as indicated in the literature [20,21,39], in that chemical decomposition (formation between the modulated phase and TiO 2 or SnO 2 -rich phases) can occur if the condition does not favor thermodynamic or equilibrium conditions, which can easily occur in the fast precipitation (less than 60 s) of the microemulsion environment.…”

“…The phase diagram for the SnO 2 -TiO 2 binary composition predicts an immiscibility domain, where favorable conditions are created for spinodal or chemical decomposition (formation between the modulated phase and TiO 2 or SnO 2 -rich phases) [16]. The substitution of Sn for Ti in the lattice structure (spinodal region) is proven to aid the formation of solid solutions, alter the structure, and contribute to the thermal stability of TiO 2 [17][18][19][20][21][22]. This may lead to an improvement in the gassensing properties.…”