On the switching dynamics of epitaxial ferroelectric CeO 2 -HfO 2 thin film capacitors.

Epitaxial layers of ferroelectric orthorhombic HfO 2 are frequently investigated as model systems for industrially more relevant polycrystalline films. The recent success in stabilizing the orthorhombic phase in the solid-solution cerium oxide - hafnium oxide system allows detailed investigations of external influences during fabrication. This report analyzes the ferroelectric properties of two thin film capacitors, which were post-deposition annealed in N 2 and O 2 atmospheres to achieve the orthorhombic phase after room temperature deposition. The samples, which exhibit very similar constituent phase, appear identical in conventional polarization-field hysteresis measurements. However, a significant switching speed difference is observed in pristine devices. Continued field cycling reduces the difference. Deeper analysis of switching transients based on the Nucleation Limited Switching model suggests that the O 2 heat treatment atmosphere results in an altered oxygen vacancy profile, which is reverted during ferroelectric cycling.