Hydroxyapatite (HA) was coated onto a titanium substrate using radio frequency magnetron sputtering. The sputtered film was crystallised by a hydrothermal treatment. The as-sputtered film and the hydrothermally treated film were observed using a canning transmission electron microscopy (STEM) equipped with energy dispersive X-ray spectroscopy (EDX). In the cross-sectional observation of the HA-Ti interface, the HA layer was crystallised after the hydrothermal treatment and the HA crystallization proceeded to near the titanium surface. In the EDX analysis the mixing layer of HA and Ti was observed at the HA-Ti interface of the as-sputtered film, and the titanium oxide layer was not observed. However, in the hydrothermally treated film, the titanium oxide layer was observed at the interface.
