In the growth process of ultrathin films of vanadium oxides on Pd(111), a s
equence of novel oxide phases with layer-dependent structures and oscillati
ng oxidation states has been detected experimentally and understood theoret
ically. These phases are interface mediated and metastable with respect to
further oxide growth. Transformation into the stable oxide configuration oc
curs beyond a critical thickness, where energetics combined with kinetic li
mitations determine the oxide multilayer structure.