RESUMO
Atom probe tomography was employed to observe and derive the composition of carbon clusters in implanted silicon. This value, which is of interest to the microelectronic industry when considering ion implantation defects, was estimated not to exceed 2 at%. This measurement has been done by fitting the distribution of first nearest neighbor distances between monoatomic carbon ions (C+ and C2+). Carbon quantification has been considerably improved through the detection of molecular ions, using lower electric field conditions as well as equal proportions of 12C and 13C. In these conditions and using another quantification method, we have shown that the carbon content in clusters approaches 50 at%. This result very likely indicates that clusters are nuclei of the SiC phase.
RESUMO
BACKGROUND: Nanostructured surface modifications of Ti-based biomaterials are moving up from a highly-promising to a successfully-implemented approach to developing safe and reliable implants. METHODS: The study's main objective is to help consolidate the knowledge and identify the more suitable experimental strategies related to TiO2 nanotubes-modified surfaces. In this sense, it proposes the thorough investigation of two optimized nanotubes morphologies in terms of their biological activity (cell cytotoxicity, alkaline phosphatase activity, alizarin red mineralization test, and cellular adhesion) and their electrochemical behavior in simulated body fluid (SBF) electrolyte. Layers of small-short and large-long nanotubes were prepared and investigated in their amorphous and crystallized states and compared to non-anodized samples. RESULTS: Results show that much more than the surface area development associated with the nanotubes' growth; it is the heat treatment-induced change from amorphous to crystalline anatase-rutile structures that ensure enhanced biological activity coupled to high corrosion resistance. CONCLUSION: Compared to both non-anodized and amorphous nanotubes layers, the crystallized nano-structures' outstanding bioactivity was related to the remarkable increase in their hydrophilic behavior, while the enhanced electrochemical stability was ascribed to the thickening of the dense rutile barrier layer at the Ti surface beneath the nanotubes.