金属铒和氟化铒掺杂的硫化锌薄膜的交流电致发光(ACEL)特性

ACEL CHARACTERISTICS OF METAL Er AND ErF3 DOPED ZnS THIN FILMS

本文报导了不同浓度的金属铒和氟化铒掺杂的硫化锌薄膜交流电致发光(ACEL)的特性,并进行了比较。实验结果表明:ZnS:ErF_3薄膜ACEL的最佳浓度(5×10^(-3)g/g)低于ZnS:Er^(3+)薄膜ACEL的最佳浓度(1×10^(-2)g/g)。在ZnS薄膜中掺入稀土离子,随着浓度的增加,稀土离子之间发生交叉弛豫,这一过程与稀土离子周围环境有关,这正是ZnS:ErF_3和ZnS:Er^(3+)薄膜ACEL具有不同的最佳浓度的主要原因。

ACEL characteristics of metal Er and ErF3 doped thin films with different doping concentration have been studied. The relation of ACEL brightness with doping concentration shows that for ACEL the optimum doping concentration of ZnS:ErF3 thin film is 5×10~3g/g. It is lower than that of ZnS:Er3 + thin film (1×10~2g/g). The emission spectra of the two samples are obviously different. At nearly the same concentration, the red emission peak is stron-ger in ZnS: ErF3 than in ZnS: Er thin film. The decay of excited state 2H11/2 is also different in two samples. At lower concentration (-10-3g/g), the decay of excited state 2H11/2 in ZnS:Er3 + thin film obeys single exponential form, but the decay of excited state 2H11/2 in ZnS:ErF3 thin film consists of two componentry-fast and 'slow exponential 'forms. We have studied the relation of latio of green emission peak to red one with applied voltage. This ratio increases with the applied voltage in' ZnS:Er3+ thin film when the concentration is low (-10~3g/g) , but remains unchanged in ZnS:ErF3 thin film. At higher concentration (~10~2g/g) this ratio decrease with applied voltage in ZnS:ErF3 thin film. Therefore, the interaction between RE ions, the cross relaxation, becomes important when the concentration gets higher. This process is affected by surroundings of RE ions. The excistence of F- ion enhances the cross relaxation process and it is the main reason why ZnS:ErF3 thin film has lower optimum concentration for ACEL. Although ErF3 'lumocen' has large impact cross section but the optimum concentration is lower. To obtain higher green ACEL thin film, ZnS:Er3+ is better than ZnS:ErF3.