  The van der Waals material CeOI is predicted to be a layered
antiferromagnetic Mott insulator by DFT+U calculation. We successfully grow the
CeOI films down to monolayer on graphene/6H-SiC(0001) substrate by using
molecular beam epitaxy. Films are studied by {\it in-situ} scanning tunneling
microscopy and spectroscopy, which shows a band gap of 4.4 eV. A metallic phase
with composition unidentified also exists. This rare earth oxyhalide adds a new
member to the two-dimensional magnetic materials.
