title: A model for the response towards oxidizing gases of photoactivated sensors based on individual SnO2 nanowires.
abstract: The paper presents a quantitative model to elucidate the role of impinging photons on the final response towards oxidizing gases of light-activated metal oxide gas sensors. The model is based on the competition between oxygen molecules in air and oxidizing target gases (such as NO(2)) for the same adsorption sites: the surface oxygen vacancies (OV). The model fairly reproduces the experimental measurements of both the steady-state and the dynamic response of individual SnO(2) nanowires towards oxidizing gases. Quantitative results indicate that: (1) at room temperature NO(2) adsorbs onto OV more avidly than oxygen; (2) the flux of photons and the NO(2) concentration determine the partition of the two gas populations at the surface; and (3) the band-to-band generation of electron-hole pairs plays a significant role in the photodesorption process of gas molecules. The model also offers a methodology to estimate some fundamental parameters, such as the adsorption rates and the photodesorption cross sections of oxidizing molecules interacting with the nanowires' surface. All these results, enabled by the use of individual nanowires, provide deep insight about how to control the response of metal oxide nanowires towards oxidizing gases, paving the way to the development and consolidation of this family of low consumption conductometric sensors operable at room temperature.
authors.affiliation: EME/XaRMAE/IN2UB, Departament d'Electrònica, Universitat de Barcelona, C/ Martí i Franquès 1, Planta 2, E-08028 Barcelona, Spain. dprades@el.ub.es
authors.forename: Joan Daniel
authors.initials: JD
authors.lastname: Prades
authors.forename: Roman
authors.initials: R
authors.lastname: Jimenez-Diaz
authors.forename: Marta
authors.initials: M
authors.lastname: Manzanares
authors.forename: Francisco
authors.initials: F
authors.lastname: Hernandez-Ramirez
authors.forename: Albert
authors.initials: A
authors.lastname: Cirera
authors.forename: Albert
authors.initials: A
authors.lastname: Romano-Rodriguez
authors.forename: Sanjay
authors.initials: S
authors.lastname: Mathur
authors.forename: Joan Ramon
authors.initials: JR
authors.lastname: Morante
mesh_terms: D005740:Gases / Q000737:chemistry*; D008956:Models, Chemical; D053770:Nanowires / Q000737:chemistry*; D009585:Nitrogen Dioxide / Q000737:chemistry; D010084:Oxidation-Reduction; D013696:Temperature; D017971:Tin Compounds / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D005740:Gases; D017971:Tin Compounds; C045358:stannic oxide; D009585:Nitrogen Dioxide