The film deposition process is described along with their morphological and structural characterizations by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-Ray diffraction (XRD) and Raman Spectroscopy. The sensing performance of the films in the detection of H2S are studied as function of the operating temperature in order to determine the maximum response to H2S. In addition, the cross-sensitivity of the films to other possible interfering toxic gases (NO2 and SO2) is evaluated.2.?Results and Discussion2.1. Morphology and Structure CharacterizationsAs evaluated by SEM pictures, the morphology of Cu-SnO2, WO3 and In2O3 films presented in Figure 1 shows a porous morphology comprising aggregates with uniform size distribution (2�C5 ��m for Cu-SnO2 and about 10 ��m for In2O3).

The WO3 films show variations in the size of the aggregates from 2 ��m to 10 ��m and this can be due to the lower deposition temperature (350 ��C) compared to the deposition temperature of the other films (400 ��C). The WO3 films deposited at 400 ��C have a more developed porosity than the films prepared at 350 ��C, but the adhesion to the substrate was poor, hence, a compromise had to be accepted. The morphology of the films deposited at a certain temperature depends mainly on the rate of evaporation, spreading, precipitation and decomposition reaction. For this reason different deposition parameters has been used for the preparation of the films (Table 1) in order to obtain porous morphology which plays an important role in the adsorption of the gas molecules [19].

The thickness of the films varies from 7 to 10 ��m as determined by film cross-section.Figure 1.SEM pictures of (a) Cu-SnO2 (b) WO3 and (c) In2O3 films.Table 1.Experimental parameters used for the film Anacetrapib deposition.Supplementary details about the deposition optimization process of the films are described elsewhere [20-22].The topographic 3D views of Cu-SnO2, WO3 and In2O3 films are shown in Figure 2. The pictures, realised on a surface of 1 ��m per 1 ��m, provide information about the shape, the size of the grains and their distribution in the aggregates. Furthermore, by means of appropriate software the mean roughness (Ra) can be calculated.

It can Brefeldin_A be seen that all the films Site URL List 1|]# have porous morphology comprising grains with sizes ranging from 100 to 250 nm. The roughness of the Cu-SnO2 seems to be the highest (21 nm), followed by In2O3 (17 nm) and WO3 (7 nm). Hence, no major differences between the films can be noted at this scale.Figure 2.3D AFM topographies of (a) Cu-SnO2 (b) WO3 and (c) In2O3 films.