Characteristics of the precursors and their thermal decomposition during the preparation of LiNbO3 thin films by the Pechini method

Lithium niobate thin films have been deposited on Pt/Ti/SiO2/Si(100) substrates by Pechini method. Characterization of the initial precursor solutions containing citric acid (CA), niobium and lithium ions has been performed by Fourier transform infrared spectroscopy, Raman spectroscopy and carbon nuclear magnetic resonance spectroscopy. The results indicate that citric acid coordinate to niobium ions to form a niobium–CA complex through one terminal carboxyl group, the hydroxyl group and the central carboxyl group as a tridentate ligand. The thermal decomposition of the Li–Nb precursors gel powder has been studied and the results show that LiNbO3 phase is formed directly from the thermal decomposition of the precursor gel. By heat-treatment at 600 °C for 2 h, polycrystalline LiNbO3 thin films with smooth and crack-free surface could be achieved.