  Two-dimensional materials offer opportunities for unravelling unprecedented
ordered states at single layer limit. Among such ordered states, Mott phase is
rarely explored. Here, we report the Mott phase in van der Waals chromium (II)
iodide (CrI2) films. High quality CrI2 films with atomically flat surface and
macro size are grown on graphitized 6H-SiC(0001) substrate by molecular beam
epitaxy. By in situ low temperature scanning tunneling microscopy and
spectroscopy (STM/STS), we reveal that the film has a band gap as large as ~3.2
eV, which is nearly thickness independent. Density functional plus dynamic mean
field theory calculations suggest that CrI2 films may be a strong Mott
insulator with a ferromagnetically ordered ground state. The Mott phase is
corroborated by the spectral band splitting, that is consistent with the
extended Hubbard model, and gap reduction at charge dopants. Our study provides
a platform for studying correlated electron states at single layer limit.
