Epitaxial undoped and Sb-doped si films have been grown on Si(001) substrates at temperatures T between 80 and 750$^{circ}C$ using energetic Si in ultra-high-vacuum Kr+-ion-beam sputter deposition(IBSD). Critical epitaxial thicknesses te, The average thickness of epitaxial layers, in undoped films were found to range from 8nm at Ts=80$^{circ}C$ to > 1.2 ${mu}$m at Ts=300$^{circ}C$ while Sb incorporation probabilities $sigma$sb varied from unity at Ts 550$^{circ}C$ to 0.1 at 750$^{circ}C$. These te and $sigma$Sb values are approximately one and one-to-three orders of magnitude, respectively, higher than reported results achieved with molecular-beam epitaxy. Plan-view and cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, channeling and axial angular-yield profiles by Rutherford back scattering spectroscopy for epitaxial Si1-x Gex(001) alloy films (0.15$leq$x$leq$0.30) demonstrated that the films are of extremely high crystalline quality. critical layer thicknesses hc the film thickness where strain relaxation starts, I these alloys wre found to increase rapidly with decreasing growth temperature. For Si0.70 Ge0.30, hc ranged from 35nm at Ts=550$^{circ}C$ to 650nm at 350$^{circ}C$ compared to an equilibrium value of 8nm.