Strontium-substituted hydroxyapatite coatings deposited via a co-deposition sputter technique

(a) SEM image shows homogeneous hydroxyapatite (HA) micro-crystallites (< 300 nm in diameter) for a HA sputter deposited coating. (b) SEM image showing more heterogeneous surface features on a Sr-substituted HA (SrHA) coating. The XPS spectra in (a) confirms the presence of a HA coating as opposed to (b) XPS spectra for a SrHA coating.