The Electrode-Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO-Based Ferroelectric Capacitors

Ferroelectric hafnium-zirconium oxide is one of the most relevant CMOS-compatible materials for next-generation, non-volatile memory devices. Nevertheless, performance reliability remains an issue. With TiN electrodes (the most reported electrode material), Hf-Zr-based ferroelectric capacitors struggle to provide reliable retention due to electrode-ferroelectric interface interactions. Although Hf-Zr-based ferroelectric capacitors are fabricated with other electrodes, the focus is predominantly directed toward obtaining a large ferroelectric response. The impact of the electrodes on data retention for these ferroelectrics remains underreported and greater insight is needed to improve device reliability. Here, a comprehensive set of electrodes are evaluated with emphasis on the core ferroelectric memory reliability metrics of endurance, retention, and imprint. Metal-ferroelectric-metal capacitors comprised of a Hf_0.5Zr_0.5O₂ layer deposited between different combinations of nitride (TiN, TiAlN, and NbN), pure metal (W), and oxide (MoO₂, RuO₂, and IrO₂) top and bottom electrodes are fabricated for the investigation. From the electrical, physical, and structural analysis, the low reactivity of the electrode with the ferroelectric is found to be key for improved reliability of the ferroelectric capacitor. This understanding of interface properties provides necessary insight for the broad implementation of Hf-Zr-based ferroelectrics in memory technology and, overall, boosts the development of next-generation memories.     

Metal Particle Composite Hardening in Ba0.85Ca0.15Ti0.90Zr0.10O3 Piezoceramics

Hard-type piezoceramics are key materials in high-power transducers and transformers. Acceptor doping is the most widely used piezoelectric hardening approach, but the mobility of oxygen vacancies at large electric fields or at high temperatures inevitably leads to the deterioration of hardening performance. The present study proposes a new hardening method associated with intragranular metal particles for achieving strong pinning of ferroelectric domain walls. Highly effective piezoelectric hardening via intragranular Ag particles in Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ ceramic is realized, where the mechanical quality factor Q_m and the coercive field E_c increase by 170% and 53%, respectively. The Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃/0.10Ag sample features a larger high-power mechanical quality factor than the pure Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃. Moreover, the piezoelectric properties (d₃₁ and k₃₁) of the Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃/0.10Ag sample show exceptional stability with the increase in vibration velocity. This composite approach of introducing metal particles can be considered as a generic hardening method and can be extended to other ferroelectric systems.     

Study on the dissolution of heat-induced ovalbumin gel in alkaline solutions relevant to the removal of fouling deposits

Heat-induced whey protein concentrate gels (HIWPCG) have previously been used to simulate milk fouling and cleaning processes. The related research has generated considerable knowledge, which is of practical interest. In the current study, heat-induced ovalbumin gels (HIOVAG) have been employed to investigate the dissolution process (related to chemical cleaning process). Both HIOVAG and HIWPCG are sensitive to NaOH solution, which is a common cleaning fluid in food industry. In contrast to the HIWPCG behavior, HIOVAG dissolution presents no optimal NaOH concentration where the rate of dissolution is highest. The dissolution temperature was found to positively influence the dissolution process of HIOVAG, i.e. the dissolution rate increased with increasing dissolution temperature. In addition, ovalbumin (OVA) concentration in HIOVAG was found to be another important factor influencing the dissolution process. However, the stirring speed (convection) and heating time had no effect in the range tested, indicating that the process was internally limited.