Mechanism of calcium disilicide-induced calcification of crystalline silicon surfaces in simulated body fluid under zero bias

A dry‐etch spark ablation method was used to produce calcium disilicide (CaSi2/Si) layers on silicon surfaces, and their biomineralization under zero bias was followed by means of scanning electron microscopy, X‐ray energy dispersive analysis, and Raman spectroscopy. CaSi2/Si wafers are bioinert at 25°C and bioactive at 37°C. Mechanistic insights regarding biomineralization were derived from an analysis of film growth morphology and chemical composition after various soaking periods in standard simulated body fluid (SBF). Changes in CaSi2 calcification behavior as a function of reaction temperature and pH, SBF concentration, and various surface modification processes were also employed for this purpose. During CaSi2/Si calcification under zero bias, calcium phosphate (CaP) growth is strongly dependent on the structural degradation of CaSi2 grains. Surface silanol groups, initially present on the as‐prepared material, cannot induce CaP nucleation, which begins only upon delamination of CaSi2 layers. The calcium phosphate phases, which are present during various growth stages, possibly include a combination of Mg‐substituted whitlockite, monetite, and tricalcium phosphate. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008