The material properties and c-Si surface passivation have been investigated for Al2O3 films deposited using thermal and plasma atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD) for temperatures (T-dep) between 25 and 400 degrees C. Optimal surface passivation by ALD Al2O3 was achieved at T-dep=150-250 degrees C with S-eff < 3 cm/s for similar to 2 cm p-type c-Si. PECVD Al2O3 provided a comparable high level of passivation for T-dep=150-300 degrees C and contained a high fixed negative charge density of similar to 6x10(12) cm(-2). Outstanding surface passivation performance was therefore obtained for thermal ALD, plasma ALD, and PECVD for a relatively wide range of Al2O3 material properties.