  The structural and electronic properties of bulk, monolayer and ultrathin
films of V$_2$O$_5$ and MoO$_3$ layered oxides have been studied with
first-principles density functional theory calculations including Van der Waals
dispersion corrections. Specific DFT+U functionals have been tested in order to
properly reproduce geometry, band-gap, static dielectric constant, and
formational enthalpies of the two materials. The mono-, and multi-layers are
cleaved along the <001> and <010> stable crystallographic orientations for V2O5
and MoO3, respectively. At least three layers are needed for both materials in
order to recover bulk-like properties. Spin-orbit effects have been
incorporated in our prediction, but they show marginal effects.
