| Zinc oxide films, a directly wide band gap semiconductor, have been actively studied because of its potential applications. It can be used in solar cells, piezoelectric device, optoelectric device, transparent conducting electrodes and gas sensors. The characteristics of ZnO films can be modulated by the appropriate dopant. To research the effects of Ge dopant on the photoluminescence of ZnO films, In this paper, we prepared Ge-doped ZnO films by alternative radio frequency magnetron sputtering and co-sputtering methods, and studied the their characteristics and luminescent properties. 1. Ge-doped ZnO films were prepared by alternative radio frequency (RF) magnetron sputtering. The influences of depositing condition on the depositing rate and annealing temperature on the film's structure and luminescent properties were studied. With increasing temperature, the intensity of the ZnO(002) diffraction peak increases, indicating that the crystalline quality of the film improves. The samples annealed at 800 and 1000℃appear the GeO and GeO2 diffraction peaks, and the intensity of the near ultra-violet emission at 395 nm increases greatly, while a weak yellow emission appears at 590 nm. The near ultra-violet emission could be attributed to the GeO color centers and exciton recombination. The yellow peak is probably related to Ge incorporated in the ZnO structure. 2. Ge-ZnO films were prepared by the co-sputtering method. The influences of different Ge content and annealing temperature on PL spectrum were studied. The PL spectrum indicated that appropriate Ge content could greatly increase the intensity of blue emission, and the annealing temperature also was an important factor affecting the luminescent spectrum. After the sample annealed at 600℃, the blue emission increase, while there were green emission. The experimental result indicated that the blue emission was probably related to Ge dopant and the green emission was possibly correlated with oxygen vacancy. |
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