Characterization of low-crystalline calcium phosphate thin films formed on silica glass surface

Low-crystalline calcium phosphate (CaP) thin films were formed on silica glass surfaces by using quasi-saturated calcium and phosphate ionic solutions at 37 degrees C. The silica glass surfaces were incubated at 37 degrees C for different periods of time to synthesize different types of CaP crystal films. An investigation on the effects that incubation time have on the chemical and physical properties of the synthesized CaP films was performed. The surface morphology of the synthesized CaP films displayed it to be highly porous. The surface roughness of the CaP films varied with incubation time, showing that the Surface roughness increased rapidly during the initial stage of incubation but remained stationary during the later periods. X-Ray photoelectron spectroscopic analysis confirmed that the film consists of calcium and phosphorus and provided detailed information on the chemical composition of the CaP films. With an increase of the incubation time, the relative amounts of calcium and phosphorus (Ca/P ratio) increased, implying that the film thickness increased. The nature of the CaP film represented by the Ca/P ratio appeared to be similar to that of octacalcium phosphate at the initial stages of formation. During the later stages of incubation, the Ca/P ratio of the film decreased to create calcium-deficient nonstoichiometric CaP crystals. These results demonstrate that the properties of CaP films can be modulated by adjusting the incubation time. Because the prepared CaP film possessed a highly porous structure, the surface area is expected to increase, which may provide more chances for adhesion molecules to adsorb onto the CaP film.