INFLUENCE OF AR PRESSURE ON RF MAGNETRON-SPUTTERED CA-5(PO4)(3)OH LAYERS

Currently, medical and dental implants are often provided with thin ca lcium phosphate ceramic coatings (preferably Ca-5(PO4)(3)OH (HA)) to i mprove their biological behaviour. Previous studies have demonstrated that radio-frequency (r.f.) magnetron sputtering is a suitable techniq ue for depositing such thin Ca-PO layers. Although X-ray diffraction s howed that the deposited films had an HA structure, the Ca/P ratio of the layers was higher than the theoretical value of 1.67 for HA. In th e present study the influence of the argon pressure and input power on the structure and chemical composition of the sputtered layers, espec ially the Ca/P ratio, is investigated. Rutherford backscattering spect rometry (RBS), stylus profilometer (alpha-step), X-ray diffraction spe ctrometry (XRD), and IR spectrometry (FTIR) were used to characterise the coatings. Although the Ca/P ratio became lower when sputtered at l ower input power, it was still higher than the value of 1.67 for HA. T he density measured for the films sputtered at 200 and 400 W did not s how a simple relation with the argon pressure. For all the films after annealing XRD and FTIR showed an HA-like structure and HE bonds. Howe ver, the OH bond appeared to be dependent on the partial pressure of w ater vapour during sputtering.