Characterization of sol-gel processing of calcium phosphate thin films on silicon substrate by FTIR spectroscopy

Calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHAp) films were obtained on silicon substrates by a sol-gel method using a spin-coating technique. In the sol-gel process, ethylendiamintetraacetic acid and 1,2-ethandiol, triethanolamine and polyvinyl alcohol were used as complexing agents and gel network forming agents, respectively. The samples were annealed at 1000 °C for 5 h in air after each spinning procedure. Spin-coating and annealing procedures were repeated 5, 8 and 10 times. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier Transform infrared spectroscopy (FTIR). FTIR-spectroscopy allowed us to predict the formation of oxyhydroxyapatite Ca10(PO4)6(OH)2-2xOx on the Si substrate. Moreover, according to the FTIR results, the side phase β-Ca3(PO4)2 has been formed instead of α-Ca3(PO4)2. In addition, the anhydrous dicalcium, phosphate phase CaHPO4 was also detected spectroscopically.