Fig. 3: The observation of OAFE Pbca phase returning to OFE Pbc21 phase after wake-up process.

a Cross-section STEM-HAADF image of the TiN/HZO/TiN device after wake-up under the bipolar triangle pulses of ±4 V, 104 cycles with f =500 kHz, in which a [010] oriented HZO O-phase grain is examined. b ABF image acquired from the green square area in a, the majority of the off-center OII atomic columns shifted along the [001] direction (green), demonstrating a Pbc21-dominated phase structure after the wake-up. The inset magnified ABF image shows the shifting direction of OII atomic columns deviating from the center of the four nearest Hf/Zr columns, fitting well with Pbc21 structure.