  Generalized ellipsometry, a non-destructive optical characterization
technique, is employed to determine geometrical structure parameters and
anisotropic dielectric properties of highly spatially coherent
three-dimensionally nanostructured thin films grown by glancing angle
deposition. The (piecewise) homogeneous biaxial layer model approach is
discussed, which can be universally applied to model the optical response of
sculptured thin films with different geometries and from diverse materials, and
structural parameters as well as effective optical properties of the
nanostructured thin films are obtained. Alternative model approaches for
slanted columnar thin films, anisotropic effective medium approximations based
on the Bruggeman formalism, are presented, which deliver results comparable to
the homogeneous biaxial layer approach and in addition provide film constituent
volume fraction parameters as well as depolarization or shape factors.
Advantages of these ellipsometry models are discussed on the example of metal
slanted columnar thin films, which have been conformally coated with a thin
passivating oxide layer by atomic layer deposition. Furthermore, the
application of an effective medium approximation approach to in-situ growth
monitoring of this anisotropic thin film functionalization process is
presented. It was found that structural parameters determined with the
presented optical model equivalents for slanted columnar thin films agree very
well with scanning electron microscope image estimates.
