Mitigation of field-driven dynamic phase evolution in ferroelectric Hf0.5Zr0.5O2 films by adopting oxygen-supplying electrode

Abstract

Ferroelectricity in (Hf,Zr)O2 films under 10 nm has been correlated with various factors, including dopant, oxygen deficiency, strain, and surface energy. Owing to their ultrathin thickness, the interfaces between the (Hf,Zr)O2 and the electrode can also influence the resultant ferroelectricity. Recently, ferroelectric (Hf,Zr)O2 fabricated on electrodes, such as Mo, showed large remanent polarization and wake-up-free behavior. However, the accurate physical/chemical mechanism behind the ferroelectric (Hf,Zr)O2 on Mo remains under debate. This study reports the structural, chemical, and electrical properties of Hf0.5Zr0.5O2 with Mo and TiN as top and bottom electrodes. The remanent polarization and coercive field of Hf0.5Zr0.5O2 with a Mo electrode (23.7 μC/cm2, 1.1 MV/cm) were higher than those with a TiN electrode (9.1 μC/cm2, 0.9 MV/cm). The X-ray diffraction analysis shows that Hf0.5Zr0.5O2 with Mo electrode exhibits a higher ferroelectric orthorhombic phase fraction than the TiN electrode, explaining its higher remanent polarization. The X-ray photoelectron and electron energy loss spectroscopies revealed that the concentration of oxygen vacancies in Hf0.5Zr0.5O2 with Mo electrode was significantly lower than that in Hf0.5Zr0.5O2 with TiN electrode, explaining the wake-up free behavior.