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 (CaSi 2 /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. CaSi 2 /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 CaSi 2 calcification behavior as a function of reaction temperature and pH, SBF concentration, and various surface modification processes were also employed for this purpose. During CaSi 2 /Si calcification under zero bias, calcium phosphate (CaP) growth is strongly dependent on the structural degradation of CaSi 2 grains. Surface silanol groups, initially present on the as‐prepared material, cannot induce CaP nucleation, which begins only upon delamination of CaSi 2 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