Vacuum ultraviolet annealing of hydroxyapatite films grown by pulsed laserdeposition

The effect of a post-deposition vacuum ultraviolet (VUV) radiation-assisted annealing treatment performed under 1 bar of oxygen at moderate temperatur es (450 degrees C) upon thin hydroxyapatite (HA) films grown by the pulsed laser deposition technique was investigated. The HA layers were deposited a t 650 degrees C under different partial oxidizing pressures without any wat er vapor and exhibited, besides the HA crystalline phase, tetracalcium phos phate and calcium oxide phases, more so for the films grown at lower oxidiz ing pressures. After the VUV-assisted anneal the layers were transformed in to high quality crystalline HA films, exhibiting Ca/P ratio values closer t o 1.67, the value for stoichiometric HA. The content of the other crystalli ne phases initially present was reduced significantly. Infrared spectroscop y also showed that the amount of OH- in the films increased after the treat ment. The combination of these two low temperature techniques opens the pos sibility of growing high quality HA layers without significant oxidation of the substrate material. (C) 1999 American Institute of Physics. [S0021-897 9(99)04012-8].