Films of Al and Al2O3 were formed by physical vapor deposition (PVD) and ion beam assisted deposition (IBAD) onto (100) Si, glass and graphite substrates. Ion to atom arrival rate (R) ratios for IBAD varied from 0.004 to 0.1 and film thicknesses varied from 150 to 1000 nm. The O/Al ratio of oxide films and the oxygen content of Al films decreased with increasing R ratio. Al incorporation into both types of films increased with R ratio up to a value of ∼4 at% at R=0.1. Al films were crystalline with a strong (111) fiber texture becoming more pronounced with increasing R ratio. Film morphology is characterized by large columnar grains at R=0, with a breakup of the columnar structure by R=0.04. Al2O3 films are amorphous under all deposition conditions. Average film stress for PVD Al2O3 films is tensile with a value of 0.68 GPa, becoming compressive at ∼1.3 eV/atom and saturating at a value of ∼-0.65 GPa at R=0.04. Indentation experiments of Al2O3/(100)Si with a 300 g Vickers indenter showed that the changes in crack length are consistent with a model in which the residual film stress is controlling.