Analysis of thin film multilayer structures by reflectance spectroscopy

The optical transfer matrix formulation was applied to the analysis of thin solid film multilayer structures used in infrared detection device technology. Our analysis is similar to optimization techniques applied to optical multilayer coatings, i.e., performing simulation of spectra and obtaining best fits to experimental spectral data (targets). We present, as a example, the application of the transfer matrix method to determine the thickness of HgCdTe films attached with epoxy to CdZnTe carriers, using normal incidence reflectance spectra. MID Infrared reflection spectra were obtained using a NICOLET Magna IR 750 Fourier Transform Infrared Spectrometer, equipped with a SPECTRATECH, Inc., microscope, taking care to operate in the linear response range of the detector. The obtained thickness values of HgCdTe films and epoxy layers agree very well with those measured by photographic techniques.