The structure and optical properties of lithium niobate thin film (LiNbO3) grown on silicon for various lanthanum concentration and molarity

We have successfully deposited lithium niobate thin films on a p-type silicon substrate (100) using Chemical Solution Deposition (CSD) method and spin coating technique. The lithium niobate thin films were doped with Lanthanum with a molarity variation of 1 M, 2 M, 3M, and 4M and concentration variation of 0%, 2%, 4%, and 6% on 2M solubility. Using reflectance data, we found that the energy gap of the niobite thin film at 1 M, 2 M, 3M, and 4M solubility are 1.36 eV, 2.79 eV, 2.38 eV, and 1.75 eV, respectively. Meanwhile, lanthanum doped lithium with concentration of 0%, 2%, 4%, and 6% yield an energy gap of 2.75 eV, 3.19 eV, 3.21 eV, and 2.45 eV, respectively. X-ray measurement on Lithium Niobate thin films show a rhombohedral structure with lattice parameter a = b while the c parameter is different.