A hot wall Atomic Layer Deposition flow reactor equipped with a Quartz Crystal Microbalance (QCM) has been used for the deposition of HfO@sub2@ thin films using tetrakis-ethylmethylamino hafnium (TEMAH) and H@sub2@O as precursors. HfO@sub2@ films were deposited on H- terminated Si, native oxide and SC1 chemical oxide. Spectroscopic ellipsometry and QCM measurements confirm linear growth of the films with a growth rate of ~1.2Å/cycle at 250°C. The films composition and morphology was examined using XPS, FTIR, AFM and XRD. Films are nearly stoichiometric HfO@sub2@ (O:Hf ~1.95) with bonded carbon content less than 3 at. % and the surface rms roughness is ~ 3% of the film thickness. A similar incubation period of ~15 cycles is found for all three starting surfaces and X-ray photoelectron emission spectroscopy shows no SiO@sub2@ formation at the interface for deposition on the H-terminated Si surfaces. However, there is evidence for Hf-O-Si bonding and RTA inert anneals (2 min in Ar) at temperatures as low as 300°C destabilize the interface and lead to the formation of interfacial SiO@sub2@. X-ray diffraction data indicate that the films start to crystallize upon anneals at 300°C. From the XPS and XRD data we conclude that initially the H termination of the surface and the as deposited amorphous HfO@sub2@ network protect the interface from oxidation. However, once the film begins to crystallize then diffusion of moisture and impurity O@sub2@ along the grain boundaries is enhanced resulting in the formation of interfacial SiO@sub2@.