Ion beam vapor deposition is a new technique to grow Si and SiGe layers on Si substrates at low temperatures. The growth of Si and SiGe layers reported in this paper involves ion-assisted dissociation of SiH4 into Si and H2 where Si is deposited. The Ge incorporation is achieved through thermal co-evaporation of elemental Ge. The SiGe films deposited at temperatures below 350 °C are planar and epitaxially grown, as confirmed by Rutherford back scattering, transmission electron microscopy, and electron diffraction analysis. The in situ cleaning is achieved by Ar ion bombardment followed by an in situ thermal annealing to repair the damage. Polycrystalline SiGe films are also deposited on substrate surfaces coated with a thin oxide.