Structural evolution and optical properties of Cd 2Nb 2O 7 films prepared by metallo-organic decomposition

Abstract

Cd 2Nb 2O 7 films were prepared by the metallo-organic decomposition process. Fused quartz supports were dip-coated in a xylene solution containing the synthesized metallo-organic precursors, cadmium di-(2-ethyl-hexanoate) and niobium tri-(ethoxy)-di-(2-ethyl-hexanoate). The deposited films were annealed at temperatures ranging from 500 to 800 °C. X-ray diffraction revealed that only the pyrochlore phase is formed at an annealing temperature of 500 °C. Raman microprobe spectroscopy was used to evaluate crystal symmetry modifications of the films caused by increasing the annealing temperature. The optical parameters of the films on fused quartz were deduced from spectrophotometric measurements. At a wavelength of 1000 nm, the refractive indices and film thicknesses were 1.75 (717±50 nm), 1.61 (1074±28 nm), 1.62 (773±193 nm), 1.68 (1048 nm) and 1.65 (2049±393 nm) for annealing temperatures of 500, 550, 600, 650 and 750 °C, respectively. The average optical energy gap was 4.3±0.1 eV. The microstructure of Cd 2Nb 2O 7 films recorded by scanning electron microscopy and atomic force microscopy were characterized by spherical aggregates with roughness of 17 nm.