Ferroelectric Properties And Polarization Fatigue Of La:Hfo2 Thin-Film Capacitors

Recently, doped HfO2 thin films have attracted considerable attention because of promising applications in complementary metal-oxide-semiconductor (CMOS)-compatible ferroelectric memories. Herein, the ferroelectric properties and polarization fatigue of La:HfO2 thin-film capacitors are reported. By varying the substrate lattice constant and film thickness, a robust remanent polarization of approximate to 16 mu C cm(-2) is achieved in a 12 nm-thick Pt/La:HfO2/La0.67Sr0.33MnO3 capacitor. Fatigue measurements are conducted using designed pulse sequences, in which the voltage, pulse width, and interval time are changed to observe the evolution of switchable polarization with increasing cycles. Severe fatigue is observed when the La:HfO2 capacitors are partially switched and the interval between the bipolar switching is elongated. These behaviors may be ascribed to the domain wall pinning scenario, in which domain switching is blocked by the migration and aggregation of charges on non-electroneutral walls. Further analysis of the fatigue behaviors with a nucleation-limited-switching model shows that the mean time and activation field for polarization switching are increased in fatigued La:HfO2 capacitors because electrical stimuli are required to disperse the aggregated charges before the domains are set free. These results facilitate the design and fabrication of HfO2-based ferroelectric memories with improved device reliability.