Thick Films on Metal Substrates

We should note that interference fringes are sometimes seen in transflection spectra. When the film is smooth but the substrate is rough, the full intensity of the beam that has been reflected from the front surface of the film will be measured at the detector. However, only a fraction of the beam that has been diffusely reflected from the substrate will be focused on the detector element. In this case, the fringes are not completely canceled, and the baseline of the transflectance spectrum exhibits a sinusoidal modulation. This effect can often be seen in the transflectance spectrum 

Fresnel reflection from the front surface of the film is usually measured along with the radiation that is transmitted through the film. The distortion of the spectrum that is caused by the Fresnel reflection will lead to deviations from Beer s law, 

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