Mechanism of Apatite Formation on Single Crystal Silicon in an Aqueous Solution at Room Temperature.

Single crystal silicon was soaked in a solution with ion concentrations 1.5 times those of human blood plasma (1.5 SBF) and a bone-like apatite layer formed on it. From analyzing the surface structural change of single crystal silicon and the composition change of solution during soaking, the mechanism of apatite formation was interpreted as follows. The single crystal silicon reacts with 1.5SBF to form a silica gel layer on its surface. The gel layer induces apatite nucleation on its surface and the apatite nuclei grow by consuming calcium and phosphate ions from 1.5SBF. By continuously supplying the ions, a dense and uniform layer of apatite with desired thickness can be formed. This method is promising for developing advanced functional medical devices such as biosensors.