Determination of thickness and optical constants of thin metal films with an extended ATR spectrum

An extended attenuated total reflection (ATR) spectrum, which consists of a surface plasmon resonance (SPR) dip and a total internal reflection (TIR) step, is used to determine the optical constant and the thickness of a thin metal film at a given frequency in the conventional Kretschmann configuration. Previous research has shown that two sets of solutions for the optical constant and thickness can be obtained from a SPR dip, and ambiguity should be removed by carrying out another angular scan process or employing a more complicated structure. However, we find that the true solution can be simply selected by a new parameter that denotes the TIR step change. Our method can avoid not only the troubles caused by the double-scan techniques but also the increased difficulties due to the existence of an additional polymer film in a single-scan method