, Volume 22, Issue 2, pp 517-534

Optical Properties of Polyimide Films in the Infrared

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The objective of this study is to determine the infrared optical constants of polyimide films in the spectral range between 2000 and 7000 cm-1using a five-oscillator Lorentz model. Model parameters are presented, in addition to the derived values of the complex refractive index and dielectric constant. The parameters were obtained using electromagnetic theory for thin films to model reflectivity data from two film samples with different thicknesses (5.17 and 12.4 μm) on gold substrates examined at two incident angles. Measurements were taken using a polarizable reflectometer device in a Fourier transform infrared (FTIR) spectrometer. The real part of the refractive index, n, is shown to be about 1.67, while the imaginary part, k, is less 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.