Many efforts have been done in order to obtain biocompatible materials (e.g. bone substitutes) with special properties (corrosion and mechanical resistance). Biocompatible materials are composed of a ceramic layer deposited on a metallic substrate. Titanium dioxide is often used as an interface layer material to increase the adhesion of the bio-material (hydroxiapatite in our case) to the metallic substrate.
Thus, in this paper, three kinds of hydroxyapatite (HA)-based films, deposited on different substrates (Si, TiO2 and HA) are presented. The first two types of samples consisting of HA/TiO2/Si and a mixture of (HA - TiO2)/Si with different TiO2 content are deposited by sol-gel and dipping method. The third type, composed of HA coatings are chemical growth from solution, by so-called Simulated Body Fluid method, which simulate the chemical environment in which the HA coatings are supposed to be used. The X-ray diffraction (XRD), Fourier transformed infra red spectroscopy (FTIR), Spectroscopic Ellipsometry (SE) and Atomic Force Microscopy (AFM) were used to investigate the growth and crystallization conditions of the films and to adjust the HA growth (adherence, stability and compatibility) in vivo. The obtained films are homogeneous and crack-free with various porosities (0-49%), wide range of refractive indices and accordingly, with the band gap in the broad range of 3.9 - 9.8 eV. Unlike, the SBF films are thinner (around 200-300 A) and non-porous. From the morphologic point of view, it has been observed the formation of HA-based films with a fine granular structure and with a grain diameter of the order of hundreds of nm for both HA-TiO2 and SBF films. The RMS roughness depends on the substrate and the deposition method and has values from few nm up to tens nm.
This work pointed out that besides sol-gel, the chemical growth from solution is also a suitable method, even better for the deposition of the nanostructured films on different substrates.