Here, we report a scanning tunneling microscopy and spectroscopy study of the growth of silicon on a tungsten diselenide (WSe2) substrate. We have found convincing experimental evidence that silicon does not remain on the WSe2 substrate but rather intercalates between the top layers of WSe2. Upon silicon deposition, the flat WSe2 surface converts into a surface with a hill-and-valley structure. The lattice constant of the hill-and-valley structure is identical to the lattice constant of WSe2 and the transition from hills to valleys is very gradual, suggesting that the top layer is composed of pristine WSe2. In order to verify this conjecture, we have removed the height information from our scanning tunneling microscopy signal and obtained chemical contrast of the surface by recording dI/dz, rather than the conventional regulation voltage of the z-piezo. The spatially resolved dI/dz maps provide compelling evidence that the deposited silicon does indeed not reside on top of the WSe2 substrate.