Blue-green and red luminescence from non-polar ZnO:Pb films

Pure zinc oxide (ZnO) and lead (Pb) doped zinc oxide (ZnO:Pb) films with different Pb doping concentrations were deposited on glass substrate by using radio frequency reactive magnetron sputtering technique. X-ray diffraction spectroscopy measurements showed that all samples with the (1 0 0) preferential orientation were growth of the non-polar. The results of X-ray photoelectron spectroscopy analysis suggested that the Pb ions were successfully doped into lattice of ZnO and the valence of Pb in the ZnO films was a mixed state of +2 and +4. Optical band gaps of the ZnO:Pb were 3.24, 2.92, 2.86 and 2.74 eV with the increase of Pb doping concentration, it could attribute this red shift phenomenon to the decrease of carrier concentration. Photoluminescence measurements showed that a broad emission band including the two blue emission peaks are about at 437 nm and 470 nm, one green and red emission peaks are about at 510 nm and 710 nm, which may compound white light. Moreover, growth of non-polar ZnO enhanced enormously the luminous efficiency of photoluminescence in our experiment. The current–voltage measurements between two surface electrodes showed the increase in resistance with increase of Pb doping concentration.