Interface effect on leakage current of ferroelectric film

• The effect of the electrode/ferroelectric interface on the leakage current in ultrathin PTO film are systematically studied using DFT calculation.
• It was found that the current of system not only depends on the electrode types but also on the interface termination of ferroelectric film.
• By further analysis, we found that the leakage current decrease following the increase of interfacial potential barrier and PTO thin film shows tunneling emission in the conduction mechanism.
• Based on this result, one can achieve a small leakage current in the preparation of ferroelectric film by constructing a proper interfacial potential barrier, which provides theoretical guidance for our experiments.

The miniaturization trend of ferroelectric memory puts forward higher requirements on the quality of ferroelectric thin films. One of the most important factors which restrict the use of ferroelectric thin films is the leakage current. The electrode and substrate show significant effects on the film leakage, in which the interface has been considered to play an important role. In order to study the interface effect on the leakage current, the transport of electrode/PbTiO3(PTO)/electrode ferroelectric capacitor was calculated by first principle method. Taking consideration of Pt, LaNiO3 electrodes and the PbO- or TiO2-terminated PTO thin film, we constructed four capacitor structures. The results indicated the current depends not only on the electrode types but also on the interface termination of film. On the whole, PTO thin film with oxide electrode has the greater current than that with metal electrode. Besides, PTO thin film with TiO2-terminated interface shows a larger leakage current than that with PbO-terminated interface. The interface barriers for the four ferroelectric capacitors were also investigated to analyze the intrinsic mechanism of interface effects. It was founded that there is an increase of leakage current following the decrease of the potential barrier and current of PTO thin film obeys tunneling emission conduction mechanism. It suggests that the interface barrier is the important factor which determines leakage and can be used to tune the electrical properties of ferroelectric films.

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