Surface nanostructuring of TiO2 thin films by high energy ion irradiation

Physical review. B, Condensed matter (Impact Factor: 3.66). 09/2010; 82(11). DOI: 10.1103/PhysRevB.82.115420


The effects of a high ion dose irradiation on TiO2 thin films under different conditions of temperature and ion nature are discussed. We have shown that anatase TiO2 thin films irradiated with N+ ions at room temperature develop a typical microstructure with mounds and voids open to the surface whereas irradiations at 700 K generate a surface pattern of well-ordered nanorods aligned with the ion beam. The formation of these patterns is caused by the simultaneous effect of ion irradiation near the film surface and a film temperature favoring the structural mobilization of the defective network of the material. To explain these phenomena, a qualitative model has been proposed and further tested by irradiating the TiO2 thin films with F+ and S+ ions under different conditions. The obtained results demonstrate that ion irradiation techniques enable the formation of tilted nanorod surface patterns with lengths of about 100 nm on anatase TiO2 thin films.

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Available from: Agustin R. Gonzalez-Elipe,
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    • "Secondly, the annealing in vacuum induces a higher electrical conductivity resulting from the existence of Ti 3þ . Ion irradiation causes loss of oxygen from the surface due to its preferential sputtering, which contributes to the formation of excess Ti 3þ [43]. Because of the existence of irradiation-induced Ti 3þ , (1) a series of Ti 3þ induced interstitial bands are formed below the conduction band minimum of TiO 2 , which would induce a strong visible light absorption; (2) an significant increase of donor density in TiO 2 is achieved, which would lead to enhanced electrical conductivity (better charge separation) [44] [48] [49]. "
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