Ferroelectric properties of HfAlO_x-based ferroelectric memristor devices for neuromorphic applications: Influence of top electrode deposition method

In this study, we compare the performance of ferroelectric memristor devices based on the fabrication method for the top electrode, focusing on atomic layer deposition (ALD) and physical vapor deposition techniques. We investigate the effects of these methods on the formation of the orthorhombic phase (o-phase) in HfAlOx (HAO) ferroelectric films, which is crucial for ferroelectric properties. The devices were fabricated with HAO films doped with 3.4% aluminum, followed by rapid thermal annealing at 700 ^̊C. Our results demonstrate that the atomic layer deposition process forms a TiOxNy capping layer at the interface between the HAO film and the TiN top electrode, which promotes the o-phase formation. This capping layer effect leads to enhanced polarization characteristics, as evidenced by higher remnant polarization and tunneling electroresistance (TER) in the ALD-fabricated devices. The ALD method also results in a better interfacial layer condition, confirmed by a lower interfacial non-ferroelectric capacitance (C_i). Characterization techniques, including transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. These structural advantages contribute to enhanced electrical performance, demonstrating neuromorphic applications. Here, our study highlights the significant impact of the ALD deposition method on enhancing the ferroelectric properties and overall performance of ferroelectric memristor devices, making it a promising approach for advanced memory and neuromorphic computing applications.