The structural development of HfO2, thin films grown from HfCl4 and water onto glass substrates by atomic layer epitaxy at 500 degrees C was studied with X-ray diffraction, atomic force microscopy and scanning electron microscopy. The films were found to contain two regions of different crystallinity : a thin amorphous starting layer and a subsequent preferentially oriented polycrystalline layer. The films were built up of densely packed grains. Substantial surface roughening occurred along with increasing film thickness. The films were chlorine free as analyzed by Rutherford backscattering spectrometry.