Optical properties of polyimide films in the infrared

The objective of this study is to determine the infrared optical constants of polyimide films in the spectral range between 2000 and 7000 cm(-1) using a five-oscillator Lorentz model. Model parameters are presented. in additi on to the derived values of the complex refractive index and dielectric con stant. The parameters were obtained using electromagnetic theory for thin f ilms to model reflectivity data from two film samples with different thickn esses (5.17 and 12.4 mum) on gold substrates examined at two incident angle s. Measurements were taken using a polarizable reflectometer device in a Fo urier transform infrared ( FTIR) spectrometer. The real part of the refract ive index, n, is show n to be about 1.67, while the imaginary part, k, is l ess than 0.01 over the spectral range examined. Results are consistent with findings of other experimentalists. and new data presented here show that polarization effects on thin film layers are predictable from the proposed model.