Combinatorial magnetron sputtering was used to generate a library of devices with a wide range of Hf:Zr ratios. The electrical properties of these devices were systematically investigated and correlated to the crystal structure. XRD, XRR, XPS, and EDS were used to measure film structure, thickness, bonding, and chemistry across the sample, respectively. Time-resolved PUND measurements were used to confirm ferroelectric behavior in devices ranging from 49 to 22 atomic % Hf. The switching current and polarization were extracted from the PUND measurements. Ferroelectricity is shown to increase from 49 to 38% Hf. Further decreasing Hf decreases the switching polarization, while also generating peak splitting behavior. Device endurance properties were measured and showed consistent switching up to 104 cycles, while enduring cycling out to 105 cycles. Increased cycling of bimodal switching unified the peak splitting, while increasing the overall switching polarization. XRD structural measurements showed high orthorhombic/tetragonal peaks in the regions exhibiting ferroelectricity, suggesting that the primary phase driving the ferroelectric behavior is orthorhombic.
Flynn‐Hepford et al. (Tue,) studied this question.