Enhancement of the ferroelectricity by interface engineering observed by in situ transmission electron microscope

Hafnia-based ferroelectrics with excellent scalability and complementary metal-oxide-semiconductor technology compatibility are potential materials for next-generation memory and logic devices. Stabilizing the metastable ferroelectric phase in hafnia-based ferroelectrics is critical for realizing technological applications. Interface engineering is a critical method to stabilize the ferroelectric phase. However, the role played by the interface between the metal electrode and the hafnia-based ferroelectrics oxide remains unclear. In this work, a typical Hf0.5Zr0.5O2 (HZO) ferroelectric oxide film sandwiched between the metal electrode and the silicon substrate was fabricated with and without the interfacial layer. By using the in situ transmission electron microscope, the atomistic structure evolution of the HZO film ferroelectric phase was studied under electrical stimuli. It is found that the phase transition from ferroelectric (FE) orthorhombic phase (O-phase) to dielectric monoclinic phase (M-phase) occurs from the interface between the HZO and the metal electrode. While in the one with Al2O3 as an interfacial layer between the HZO and the metal electrode, the FE O-phase could remain without phase transition. This work shows the microscopic view to enhance the ferroelectric evolution in HfO2-based devices.