No abstract

No abstract

No abstract

No abstract

The two images produced by each feature in a Nomarski polarization interferogram are in general not equivalent. In the case of an etch pit or other isolated, sloped feature, the angle ϑ between the feature and the flat background surface can be computed from the fringe spacing l in the feature by the relationship sin[ϑapp−(ε/2) cosα] =λ/2l. The angle ε/2 is calculated from the background fringe spacing l0 and the relation sin(ε/2) =λ/2l0. The angle α is the orientation of the feature with respect to the background interference fringes on the flat surface. An additional correction is necessary to calculate ϑ from ϑapp because of the distortion of the fringe spacings which occurs in microinterferometers when using microscope objectives of large numerical aperture. Empirical observation shows that this obliquity correction can be calculated accurately by a formula first derived by Ingelstam. The method of determining slopes from fringe spacings in Nomarski polarization interferometry is described in detail. This description may be of interest to investigators who study crystal surfaces or changes in their topography during chemical reactions, because the Nomarski microinterferometer is suitable for continuous observation of surface changes which accompany reactions in a controlled-atmosphere heating stage.