  Two-dimensional electron systems (2DES) 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
sub-band 2DES can be prepared in thin films of Bi2O2Se, where the film
thickness acts as the sole design parameter and the sub-band occupation is
determined by the electric field effect. This new 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.
