Zigzag domain walls unravel the polarization switching puzzle in wurtzite ferroelectrics

• The broad transitional regions observed in STEM during polarization switching in wurtzite ferroelectrics are projection artifacts, not a transient nonpolar phase. • 180° domain walls in AlScN are intrinsically three-dimensional and adopt a zigzag morphology, which explains the apparent diffuse interfaces in 2D imaging. • The zigzag inversion domain boundary (IDB*) model consistently explains all experimental observations, including high coercive fields and switching kinetics. • Integration of advanced thin-film fabrication, electrical characterization, and deep neural network-based molecular dynamics simulations resolved the long-standing polarization switching puzzle.