Quantum Hall effect in a CVD-grown oxide

Two-dimensional (2D) electron systems are promising for investigating correlated quantum phenomena. In particular, 2D oxides provide a platform that can host various quantum phases such as quantized Hall effect, superconductivity, or magnetism. The realization of such quantum phases in 2D oxides heavily relies on dedicated heterostructure growths. Here we show the integer quantum Hall effect achieved in chemical vapor deposition grown Bi₂O₂Se - a representative member of a more accessible oxide family. A single or few subband 2D electron system can be prepared in thin films of Bi₂O₂Se, where the film thickness acts as the key subband design parameter and the occupation is determined by the electric field effect. This oxide platform exhibits characteristic advantages in structural flexibility due to its layered nature, making it suitable for scalable growth. The unique small mass distinguishes Bi₂O₂Se from other high-mobility oxides, providing a new platform for exploring quantum Hall physics in 2D oxides.