It means that probably the small amount of residual oxygen is only weakly (physically) bounded at the surface of SnO2 nanowires. It corresponds to a small increase of relative [O]/[Sn] concentration after TDS process, as evidenced from XPS measurements. Concerning the case of water vapor (H2O), there is a maximum GSI-IX price relative partial pressure of about 10-8 mbar at about 170°C, as can be seen from the respective TDS spectrum. This is quite similar to one of the molecular oxygen (O2)

with a different value of maximum partial pressure (almost one order of magnitude higher). The most important TPD effect was observed for carbon dioxide (CO2). The respective TDS spectrum exhibit a more complicated shape with two evident peaks: a wider one, having a maximum of relative partial pressure of about 10-9 mbar

BKM120 nmr at about 200°C, and a narrow one, having a maximum partial pressure slightly smaller at about 350°C. It probably means that C containing surface contaminations is bounded in two different forms and with different bonding energy at the external surface of crystalline SnO2 nanowires. These last observations related to the desorption behavior of water vapor (H2O) and carbon dioxide (CO2) were in a good correlation with an evident increase of relative [O]/[Sn] concentration, as well as almost complete vanishing C contaminations from the nanowires

under investigations as determined cAMP by the XPS experiments. Thanks to the complete removal of C contaminations during TPD process the surface of SnO2 nanowires became almost stoichiometric, in a good agreement to the published electron diffraction data [22]. Additionally, TEM analysis [20, 23] of SnO2 nanowires showed that these one-dimensional nanostructures are single crystals with atomically sharp terminations. They have the SnO2 BIIB057 datasheet cassiterite structure and grow along the [101] direction. The SEM images in Figure 4 report the morphology of SnO2 nanowires. Moreover, it is easy to estimate that the ratio between their length (several microns) and width (less than 100 nm) is very high. Figure 4 SEM images of SnO 2 nanowires of different magnification. All information reported above are crucial for potential application of SnO2 nanowires in the detection of C containing species. The last one, i.e., that there is a possibility to complete removal of C contaminations during TPD process from the surface of SnO2 nanowires, is of great importance because it allows to get shorter response/recovery time for the gas sensors systems based on SnO2 nanowires. This is in evident contradiction to the observation for the SnO2 thin films, as summarized in [5]. Conclusions SnO2 nanowires have been synthetized on Ag-covered Si (100) substrate by VPD technique.