Of course, this observation looks as critical because H2 can affect the sensing mechanism at the surface of SnO2 gas sensors leading to a reduction of the SnO2. However, we did not observe this effect, probably for two reasons. Firstly, the relative molecular hydrogen Temsirolimus research buy partial pressure we observed during the registration of our TDS spectra is evidently Nutlin-3a mw smaller in comparison to the typical concentration
in gas sensor experiments (parts per million level). Secondly, a reduction of the SnO2 by H2 can only be observed at evidently higher working temperature, as also observed in [12]. Moreover, from the TDS spectra shown in Figure 4, it is visible that apart from H2, the water vapor (H2O) and carbon dioxide (CO2) mainly desorbed from the air exposed Ag-covered L-CVD SnO2 nanolayers. For H2O the highest relative partial pressure at the level of 7 × 10−8 mbar at about 180°C was observed and was one order of magnitude smaller than for the case of H2. In turn for CO2, there is a wider range of desorption temperature (150°C ÷ 240°C), and the highest relative partial pressure of about 6 × 10−8 mbar was observed at about 220°C.
This probably means that C-containing surface contaminations are more strongly bounded to the internal surface of the air exposed Ag-covered L-CVD Crenolanib purchase SnO2 nanolayers. This last observation was in a good correlation with an evident decrease (by factor of 3) of C contaminations from these nanolayers as determined by the subsequent XPS experiments (see Figures 1 and 3). However, Paclitaxel cost at this point it should be additionally explained that we have registered the TDS spectra only up to 350°C, because even higher temperature does not allow the complete removing of C from the surface of L-CVD SnO2 nanolayers. Instead, in such a condition
the C exhibits a tendency to uncontrolled and undesired diffusion to L-CVD SnO2 nanolayers observed in our recent XPS depth profiling studies [6]. According to our observation, a common approach observed in literature is mistakenly neglecting a role of C contamination at the surface and inside the SnO2 thin films working as the gas sensors to different oxidizing gases. This is crucial, since these gases strongly affect the sensing mechanism at the surface of SnO2 gas sensors working in normal conditions. This is probably a reason that the highest sensitivity of SnO2 gas sensors is observed at about 200°C. Finally, also the molecular oxygen (O2) desorbs from the air-exposed Ag-covered L-CVD SnO2 nanolayers during the registration of TDS spectra. However, at the evidently lowest partial pressure varying within one order of magnitude and reaching a maximum value of about 4 × 10−9 mbar at about 180°C. It means that the molecular oxygen (O2) is also rather weakly (physically) bounded at the internal surface of the air-exposed Ag-covered L-CVD SnO2 nanolayers.