Excimer laser deposition of hydroxyapatite thin films.

We have demonstrated a new and simple in situ method to fabricate adherent and dense hydroxyapatite (HA) coatings at relatively low deposition temperatures (500-600 degrees C). Under optimum processing conditions, the HA coatings possess a nominal Ca:P ratio of 1.65 and exhibit a fully crystalline single-phase structure. This deposition technique is based on the application of a pulsed excimer laser (wavelength lambda = 248 nm, pulse duration tau = 25 x 10(-9) s) to ablate a dense stoichiometric HA target. The HA target was prepared by standard ceramic coprecipitation techniques followed by cold pressing and further sintering at 1200 degrees C in air. High substrate temperatures (> or = 600 degrees C) during film deposition led to phosphorus deficient coatings because of re-evaporation of phosphorus during the deposition process. The stabilization of various calcium and phosphorus phases in the film was controlled by a number of process parameters such as substrate temperature, chamber pressure and presence of water vapour in the chamber. This is particularly advantageous for production of HA coatings, since it is known that HA decomposes at high temperatures due to the uncertainty in the starting material stoichiometry. Rutherford backscattering spectrometry, energy dispersive X-ray analysis, transmission electron microscopy, scanning electron microscopy and X-ray diffraction techniques were employed to determine the structure-processing relationships. Qualitative scratch measurements were conducted to determine the adhesion strength of the films.

[1]  B. L. Barthell,et al.  Ion Beam Deposition of Calcium Hydroxyapatite , 1987 .

[2]  Jagdish Narayan,et al.  Theoretical model for deposition of superconducting thin films using pulsed laser evaporation technique , 1990 .

[3]  P. Holloway,et al.  Laser‐target interactions during pulsed laser deposition of superconducting thin films , 1991 .

[4]  C. Klein,et al.  Plasma sprayed coatings of hydroxylapatite. , 1987, Journal of biomedical materials research.

[5]  P. Ducheyne,et al.  Plasma spraying induced changes of calcium phosphate ceramic characteristics and the effect onin vitro stability , 1992 .

[6]  Narayan,et al.  Pulsed-laser evaporation technique for deposition of thin films: Physics and theoretical model. , 1990, Physical review. B, Condensed matter.

[7]  E. Ruckenstein,et al.  A nondestructive approach to characterize deposits on various surfaces , 1983 .

[8]  J. Featherstone,et al.  Crystallographic changes in calcium phosphates during plasma-spraying. , 1992, Biomaterials.

[9]  P Ducheyne,et al.  Calcium phosphate ceramic coatings on porous titanium: effect of structure and composition on electrophoretic deposition, vacuum sintering and in vitro dissolution. , 1990, Biomaterials.

[10]  H. Oguchi,et al.  Evaluation of a high-velocity flame-spraying technique for hydroxyapatite. , 1992, Biomaterials.

[11]  M. Lutwyche,et al.  Laser wavelength dependent properties of YBa2Cu3O7−δ thin films deposited by laser ablation , 1989 .

[12]  D. Chrisey,et al.  Pulsed laser deposition of hydroxylapatite thin films on Ti‐6Al‐4V , 1992 .