The analytical dependence of σn and σk on related experimental uncertainties when conventional reflectance–transmittance methods for the determination of optical constants of thin films are used has been found. Two kinds of singularity appear. These are responsible for the loss of solution in these methods. From the properties of the derivatives of n and k with respect to the measured thickness, a new method has been developed without loss of solution. Different derivative behaviors for physical and nonphysical solutions were found. The film thickness is also determined by this method with an accuracy better than 0.2%. The method has been applied to thin films of amorphous germanium.
© 1992 Optical Society of America
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