Giant enhancement of ultraviolet near-band-edge emission from a wide-bandgap oxide with dipole-forbidden bandgap transition

We report giant enhancement of recovered ultraviolet near-band-edge emission from SnO2 thin films with dipole-forbidden bandgap transition via Ag-doping and surface plasmon coupling. It is found that a recovering near-band-edge emission in the range of 361-375 nm in a low-concentration Ag-doped SnO2 film, suggesting that dipole-forbidden transition rule of SnO2 is broken. First-principles electronic structure calculations indicate that the breaking of the dipole-forbidden transition rule is derived from the acceptor of Ag substituting Sn in SnO2. 30-fold enhancement of ultraviolet near-band-edge emission from the Ag-doped SnO2 film is observed by modifying film surface using Ag nanoparticles. The giant enhancement of ultraviolet emission is ascribed to surface plasmon coupling between Ag-doped SnO2 and Ag nanoparticles. Our results suggest that Ag doping and Ag nanoparticles surface modification in SnO2 films play important roles in recovering and enhancing ultraviolet emission of SnO2 with dipole-forbidden bandgap transition.