Energy transfer up-conversion of Tm,Yb-codoped ZnO grown on ZnO nanowires by sputtering-assisted metalorganic chemical vapor deposition

Abstract We report on the optical characteristics of Tm,Yb-codoped ZnO (ZnO:Tm,Yb) films on ZnO nanowires (NWs). ZnO:Tm,Yb films with controlled concentration ratios of Tm 3+ and Yb 3+ are grown on the ZnO NWs by sputtering-assisted metalorganic chemical vapor deposition. Characteristic luminescence due to intra-4f shell transitions of Tm 3+ and Yb 3+ in the ZnO host is observed at 5 K via photoluminescence (PL) characterization. The PL characterization under both indirect and direct excitation of rare earth ions reveals the occurrence of energy transfer up-conversion from Yb 3+ to Tm 3+ . Phonon-assisted energy transfer is identified as the dominant process for up-conversion in the ZnO:Tm,Yb by performing detailed optical characterization including the dependence of excitation wavelength and power.