Ellipsometry-transmission measurement of the complex refractive indices for a series of organic solvents in the 200–1700 nm spectral range

Abstract

Organic solvents are fluids commonly used in different branches of materials science. The determination of the wavelength-dependent complex refractive index of organic solvents is essential in physical, chemical, biological, and optical applications. The existing databases for the complex refractive index of many organic solvents are insufficient and have low accuracy, particularly in the ultraviolet (UV), visible (Vis), and near-infrared (NIR) spectral ranges. In this work, using spectroscopic ellipsometry combined with the transmission method, the complex refractive indices of isopropyl acetate (IPAC), dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-dimethylaniline (DMA), dichloromethane (DCM), tetrahydrofuran (THF), P-Xylene (PX), and ethyl acetate (EA) were measured in the spectral range 200–1700 nm at room temperature and ambient pressure. The refractive index and absorption index were measured by the ellipsometry and transmission method, respectively, allowing accurate measurement of the complex refractive index of materials with weak optical absorption. Based on these experimental data, the refractive indices in the weak absorption waveband were fitted using Cauchy’s dispersion formula. According to the dispersion relationships and molecular structure of each solvent, it is known that the addition of benzene rings, sulfur atoms, chlorine atoms, nitrogen atoms, and epoxides can increase the refractive index of a material. The results obtained in our laboratory for organic solvents provide evidence that the ellipsometry-transmission method is a promising technique for characterizing the optical constants of different types of materials. The experimental data of the complex refractive indices and their dispersion of organic solvents can provide a reference for its practical applications.