Direct_DF: Dielectric functions from
reflectance and transmittance spectra
Purpose
For spectral ranges where you can measure reflectance and transmittance at normal incidence of light the dielectric function can be directly evaluated if the thickness is known. The spectra must not contain interference fringes. These are very narrow for thick samples and are in many cases not resolved by the spectrometer. Thickness variations over the investigated sample spot and the beam divergence may also be reasons why no interference patterns are observed.
If a sample meets the above requirements the way to proceed is straightforward. Record reflectance and transmittance spectra, import them into the Direct_df software, enter the thickness and press the update button. That's it.
A step-by-step example is given in the following section.