文摘
We irradiated SnO<sub>2sub> nanowires with He ions (45 MeV) with different ion fluences. Structure and morphology of the SnO<sub>2sub> nanowires did not undergo noticeable changes upon ion-beam irradiation. Chemical equilibrium in SnO<sub>2sub>/gas systems was calculated from thermodynamic principles, which were used to study the sensing selectivity of the tested gases, demonstrating the selective sensitivity of the SnO<sub>2sub> surface to NO<sub>2sub> gas. Being different from other gases, including H<sub>2sub>, ethanol, acetone, SO<sub>2sub>, and NH<sub>3sub>, the sensor response to NO<sub>2sub> gas significantly increases as the ion fluence increases, showing a maximum under an ion fluence of 1 × 10<sup>16sup> ions/cm<sup>2sup>. Photoluminescence analysis shows that the relative intensity of the peak at 2.1 eV to the peak at 2.5 eV increases upon ion-beam irradiation, suggesting that structural defects and/or tin interstitials have been generated. X-ray photoelectron spectroscopy indicated that the ionic ratio of Sn<sup>2+/sup>Sn<sup>4+sup> increases by the ion-beam irradiation, supporting the formation of surface Sn interstitials. Using thermodynamic calculations, we explained the observed selective sensing behavior. A molecular level model was also established for the adsorption of NO<sub>2sub> on ion-irradiated SnO<sub>2sub> (110) surfaces. We propose that the adsorption of NO<sub>2sub>-related species is considerably enhanced by the generation of surface defects that are comprised of Sn interstitials.
