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A MIM thin film diode (TFD) with Ta-Ta2O5-Ta symmetrical structure for active-matrix liquid crystal display (AM-LCD) was prepared. The Ta2O5 insulator layer as a key to the MIM thin film diode was got by anodizing sputtered tantalum oxide film (sputtering/anodization two-step process), and was heat-treated by vacuum/atmosphere two-step heat- treatment with different process parameter. The microstructure of tantalum oxide film was analyzed by Atomic Force Microscope (AFM) and Transmitting Electron Microscope (TEM), respectively. The I-V characteristics of the MIM thin film diode were also measured. The influence of heat-treatment on microstructure of Ta2O5 insulator film and the I-V characteristics of the MIM thin film diode were investigated. The relationship between the I-V characteristics of the MIM thin film diode and microstructure of Ta2O5 film was also indicated. The results showed that the Ta2O5 film sample with vacuum/330 degree(s)C atmosphere two-step heat- treatment had uniform and dense amorphous microstructure, and had a good stability, a high switching-on/off ratio (105), and excellent symmetric I-V characteristics with the positive and negative threshold voltages 7V and 6.6V, respectively, and little relative errors (< 6%). The properties of this MIM- TFD can meet the needs of AM-LCD.
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