The influence of the deposition parameters on the properties of an rf-magnetron-deposited nanostructured calcium phosphate coating and a possible growth mechanism

The deposition of a biocompatible calcium phosphate coating on the surface of materials for biomedical implants by rf-magnetron sputtering is reported. The deposition parameters to prepare either stoichiometric crystalline hydroxyapatite or amorphous calcium phosphate coating with a molar Ca/P ratio from 1.53 to 3.88 were established. Crystalline hydroxyapatite coating with a Ca/P ratio of 1.60 ± 0.07 can be deposited if the rf-power density is 0.49 W cm­2 and if the samples are arranged within the area of the target erosion zone. A thorough investigation of the influence of rf-power, DC-bias on the substrate, deposition time on the properties of the calcium phosphate coating allowed to formulate a mechanism for the film growth.