Of Bst Pyroelectric Thin Film Leakage Current Characteristics And Soft Breakdown Characteristics

Ba_xSr_1-xTiO₃(BST)thin films were widely applied in ultra-high density integrated DRAM, microwave tunable devices, and uncooled infrared detector, due to its high dielectric permittivity, low dielectric loss, variable Curie temperature, and good pyroelectric properties. In devices, BST thin film was applied DC voltage, the leakage current in the films would increase with the creasing of applied voltage time, till soft breakdown phenomenon occurring, which impact seriously on the stability and lifetime of devices. In this dissertation, BST thin films were deposited by radio frequency sputtering on Pt/Ti/SiO₂/Si substrates. The leakage current mechanisms of BST thin films were investigated by measuring the I - V characteristics. Furthermore, the relationships between the preparing conditions and the leakage current characteristics, and the soft breakdown properties of the thin films were investigated. Firstly, the precise I ? V curves of BST thin films were obtained by measuring the I - t curves under various electric field. The results indicate, the leakage current obeys Ohm's law in low electric field, and is consistent with space charge limited current in high electric field.Secondly, the I ? t characteristics of BST thin film prepared with different buffer processes were investigated, the relationships between preparing processes of thin films and the leakage current characteristics were obtained, and the optimal preparing processes of buffer were given.Thirdly, the current transient phenomenon was observed, which results from the cumulation of oxygen vacancy at the electrode/BST interface, in the Ni-Cr/BST/SRO samples. The current transient phenomenon can be renewed under a appropriate reverse voltage with proper time.Lastly, the soft breakdown properties were investigated under various voltages and at temperatures ranging from 25℃to 125℃. The breakdown time decreases with the increase of temperature, and exponentially decreases with increasing applied voltage. The mechanism of soft breakdown of BST thin films was discussed.