We report the results of grazing incidence small angle x-ray scattering experiments on the nucleation and growth of atomic layer deposited HfO2 films. The scattering features are internal (porosity) and external (roughness) surfaces. Films grown on H-terminated Si exhibit greater scattering than films grown on chemically oxidized Si. The films grown on H-terminated Si may be as much as 50% porous. Characteristic scattering feature sizes are those of the film nuclei, about 2 nm, which then coalesce and become inherited features of the films. Films grown on chemically oxidized Si are observed to coalesce at about 25 growth cycles.