Atomic-Scale Characterization of Negative Differential Resistance in Ferroelectric Bi2WO6

Negative differential resistance (NDR), a quantum nonlinear electron transport process, has long attracted research interest owing to its intriguing underlying physics and promising applications in high-speed electronics. Here, the authors report the NDR behavior in (001)-oriented ferroelectric Bi2WO6 using scanning tunneling microscopy (STM). The current-voltage characteristics of the diode configuration consisting of an STM tip over the [BiO](+)-[WO4](2-)-[BiO](+) terrace exhibit NDR features. Scanning tunneling spectroscopy combined with density functional theory calculations indicates that the observed NDR results from robust resonant tunneling through confined energy levels within the 2D [WO4](2-) layer. The atomically resolved NDR found in such a transition metal oxide offers a unique band structure for novel ferroelectric-based devices.