Electrically Switchable Polarization in Bi 2 O 2 Se Ferroelectric Semiconductors.

Atomically 2D layered ferroelectric semiconductors, in which the polarization switching process occurs within the channel material itself, offer a new material platform that can drive electronic components toward structural simplification and high-density integration. Here, a room-temperature 2D layered ferroelectric semiconductor, bismuth oxychalcogenides (Bi 2 O 2 Se), is investigated with a thickness down to 7.3 nm (≈12 layers) and piezoelectric coefficient (d 33 ) of 4.4 ± 0.1 pm V -1 . The random orientations and electrically dependent polarization of the dipoles in Bi 2 O 2 Se are separately uncovered owing to the structural symmetry-breaking at room temperature. Specifically, the interplay between ferroelectricity and semiconducting characteristics of Bi 2 O 2 Se is explored on device-level operation, revealing the hysteresis behavior and memory window (MW) formation. Leveraging the ferroelectric polarization originating from Bi 2 O 2 Se, the fabricated device exhibits "smart" photoresponse tunability and excellent electronic characteristics, e.g., a high on/off current ratio > 10 4 and a large MW to the sweeping range of 47% at V GS  = ±5 V. These results demonstrate the synergistic combination of ferroelectricity with semiconducting characteristics in Bi 2 O 2 Se, laying the foundation for integrating sensing, logic, and memory functions into a single material system that can overcome the bottlenecks in von Neumann architecture.