Pulsed-laser deposition of hydroxyapatite thin layer on Ti alloy collectors with and without buffer interlayers

Abstract

Hydroxyapatite (HA), Ca<SUB>10</SUB>(PO<SUB>4</SUB>)<SUB>6</SUB>(OH)<SUB>2</SUB>, is the best substitute of the human bone. On the other hand, HA stands for more than 70% from the composition of the bone tissue. We note for HA is friable. Accordingly, it exhibits a very poor mechanical tenure and cannot be used as bulk ceramic for the manufacturing of prostheses. A solution was conceived to surpass this difficulty which resorts to the deposition of HA thin layers on prostheses or pivots of Ti and Ti alloys. The biological tissues enter under these conditions in contact with HA which is perfectly biocompatible. We previously performed Pulsed Laser Deposition (PLD) experiments on Ti, KCl and KBr substrates. We obtained the stoichiometric transfer of HA by PLD in vacuum or by RPLD in (1 - 50) Pa of oxygen, followed by a heat treatment in air. We use an excimer laser source ((lambda) equals 248 nm, (tau) <SUB>FWHM</SUB> &gt;= 20 ns). The incident laser fluence was set an 0.8 Jcm<SUP>-2</SUP>. We report herewith the deposition of a more elaborate structure introducing a buffer interlayer between the Ti substrate and the HA coating in order to improve the quality of HA films and to prevent the diffusion of metal atoms into the deposited layer. The layer was obtained by RPLD from a Ti target in a slow flux of air having a dynamic pressure between the range (4 - 6) Pa. The deposited structures were characterized by electron microscopy (TEM, SAED), X-ray diffraction (XRD) and energy disversive X-ray spectroscopy (EDS) analyses.