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학위논문 동서

Zns:Mn:Cu박막 EL소자의 제작 및 발광기구 해석에 관한 연구

강정호

부산: 동아대학교 1997. -

i,83장: 삽도; 26cm. -

학위논문(박사)- 동아대학교 대학원 전자공학과 1997년2월

영문초록 : Among the various flat panel display devices the Electroluminescence Display (ELD) is the one which has been widely researched because of the superior relative brightness and the possibility of large area device and the fast response. In this paper ELD which is able to generate the green and the blue light depending on the applied bias has been fabricated. ZnS was used as the phosphor and as the actuator Cu and Mn were used. The phosphor was sandwiched between Y_(2)O_(3) insulator and the simple fabrication process has been developed by using the evaporator. Finally the new theoretical models for the spectrum of the produced light and the pulse response have been proposed and proved by the experiment. For the theoretical model the various models have been published but their applications are limited. In this paper a new model for the spectrum of the output light has been proposed. The model employed the gas laser theory, which can be justified because the density of actuator as the source of light generation is as rare as the gas laser. In this model the bandwidth of the spectrum was identified due to the energy scattering between the electrons and the actuators. The spectrum of the fabricated ELD was identical to that of the model where the peak was located at 540 nm of green light. The conventional model for the pulse response was also modified to be applicable to the structure of ELD which was fabricated in this paper. In this model the electrons captured at the interface states between the phosphor, ZnS and the insulator, Y_(2)O(3) are ionized and accelerated in the phosphor by the applied electric field. The energetic electrons excite the electrons at the energy level of Cu to the conduction band (ΔE=2.97eV) or the electrons at the low energy level to the high level of Mn(ΔE=2.37eV) depending on the applied voltage. The excited electrons generate blue or green light depending on the energy difference (ΔE) by returning to the initial level. When the energetic electrons reach the other interface, they are captured again by the interface states resulting in ionizing the states and reducing the applied field. Thus the generation of light reduces with time. Such mechanism was identified by the experiment where the square wave of voltage was applied to the device and the generation of light and the reduction of brightness with time was observed. ELD consists of ZnS phosphor which is doped by Cu (0.05Wt%) and Mn (0.5Wt%) and sandwiched between Y_(2)O(3) insulator at both sides. ITO and Al were used for the metal contacts. In this paper the simple fabrication process was developed, where ZnS phosphor (6000~8000Å) and Y_(2)O_(3) insulator (2000~3000Å) as well as al metal (1000Å) were evaporated in the same chamber. The crystal structure of ZnS phosphor depends on the thickness and the deposition rate and annealing conditions. The optimal conditions are 8000Å for the thickness of phosphor and 130~250Å/min for the deposition rate and 900℃/2hr for the annealing. For the condition the threshold voltage was 50V and the brightness increased with the frequency of the applied voltage. The peak wavelength of the spectrum was 540nm of the green light. For the study of ZnS ELD doped by Cu and Mn the conclusions are as follows 1) A new theoretical model for the spectrum of the output light and the pulse response was developed employing the gas laser theory, whose validity was proved by the experiment. 2) A simple fabrication process, which used the evaporator to deposit ZnS phosphor and Y_(2)O_(3) insulator and Al metal in the same chamber, was developed. 3) The optimal conditions for the low threshold voltage (50V) sustaining the high relative brightness were extracted for ZnS phosphor; 8000Å for the thickness and 130~250Å/min for the deposition rate and 900℃/2hr for the annealing.

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