| Abstract
| - The thermal evolution of sol−gel SnO2-based thin films was explored by investigatingtheir structural and morphological features. Nanostructured SnO2 and Pt-doped SnO2 layerswere obtained using tetra(tert-butoxy)tin(IV) and Pt(II) acetlylacetonate as precursors. Filmswere prepared by spin coating from ethanol solutions with different viscosity. After dryingat room temperature, they were annealed in air at 673 and 973 K. The surface morphologywas analyzed by scanning electron microscopy, atomic force microscopy, and scanning near-field optical microscopy. The structural characterization was performed by means of glancingincidence X-ray diffraction and microdiffraction. Both drying at room temperature andthermal treatment at 673 K resulted in the formation of holes on the surface and inside thefilms. Their distribution and average dimension were found to depend mainly on the viscosityof the sol precursor, and on the presence of Pt in the films. After annealing at 973 K, surfacesegregation of PtOx phases and partial filling of the surface holes occurred. The effects ofmorphology on the electrical transport properties are discussed on the basis of sensitivity,S, measurements (S = Rair/RCO, where Rair and RCO stand for the resistance in air and CO/air, respectively).
- The formation of 200−400-nm-diameter surface holes is related to the viscosity of the ethanol solution of tetra(tert-butoxy)tin(IV) and Pt(II) acetlylacetonate when this is used to obtain nanostructured thin layers of Pt-doped SnO2. A high electrical sensitivity parallels the increase of surface holes.
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