Influence of Cr Doping on the Morphology and Luminescence of SnO₂ Nanostructures

Cr doped nanostructures in forms of wires, belts, zigzags, and boomerangs have been fabricated by a vapor–solid method using metallic Sn and Cr 2 O 3 as precursors. A concentration of Cr of around 1 at. % has been estimated in the nanostructures by energy dispersive X-ray spectroscopy. The presence of Cr modifies the morphology of the as-grown nanostructures by promoting lateral growths and stepped features. Cr doping induces slight changes in the Raman signal, as the enhancement of the 721 cm –1 mode associated with lattice disorder. The luminescence of SnO 2 can be also modified by Cr doping. A new emission centered at 1.5 eV has been found in the Cr doped nanostructures, and its origin is discussed in this work. Cr doping also promotes an increase of the luminescence associated with oxygen vacancies (1.94 eV). X-ray absorption spectroscopy carried out at a synchrotron facility confirms that Cr is incorporated in the rutile lattices as Cr 4+; however a low presence of Cr 3+ has been also confirmed by cathodoluminescence.