Leakage mechanism in ferroelectric Hf0.5Zr0.5O2 epitaxial thin films

Fluorite-structured Hf0.5Zr0.5O2 (HZO) thin films have attracted considerable attention in recent years because of their good CMOS-compatibility and robust ferroelectricity down to a thickness of few unit-cell. The main challenges remaining to be overcome before HZO films will be the ideal candidates for next-generation, non-volatile ferroelectric memory devices are lowering its leakage current and improving its fatigue endurance. However, the leakage mechanism of the ferroelectric HZO thin films still remains elusive, which hinders the applicability of HZO in microelectronic devices. Herein, we studied the electric properties of Pt/HZO/ La0.7Sr0.3MnO3 (LSMO) heterostructures grown on (001) SrTiO3 (STO) substrates. The leakage mechanism is found to be dominated by Schottky emission and the Schottky barrier heights are 0.48 eV and 0.58 eV for Pt/HZO and LSMO/HZO interfaces, respectively. In turn, by post-annealing in oxygen atmosphere, we are able to increase the barrier height by 0.1 eV and thus effectively reduce the leakage current and improve the endurance by an order of magnitude. Our studies help guide future work to integrate HZO thin films into microelectronic devices.