TRANSMISSION-MODE PERPENDICULAR INCIDENCE ELLIPSOMETRY OF ANISOTROPICTHIN-FILMS

We show that transmission-mode perpendicular incidence ellipsometry, w hich yields the trivial values PSI = 45-degrees, DELTA = 0 for an isot ropic thin film, can be used to provide useful data during the vacuum deposition of anisotropic coatings. Thus the number of quarter-wave fi lm thicknesses necessary for a quarter-wave retardation plate can be d etermined simply by counting interference modulations on a DELTA versu s PSI graph, and the material property DELTAn, the difference between the slow and fast axis refractive indices, is available from the gradi ent of a smoothed DELTA versus thickness graph. The influences of diff erential absorption, differential refractive index inhomogeneity, and instrumental errors on the ellipsometric parameters are discussed.