  Surface waves, named here as Dyakonov-Tamm waves, can exist at the planar
interface of an isotropic dielectric material and a chiral sculptured thin film
(STF). Due to the periodic nonhomogeneity of a chiral STF, the range of the
refractive index of the isotropic material is smaller but the range of the
propagation direction in the interface plane is much larger, in comparison to
those for the existence of Dyakonov waves at the planar interface of an
isotropic dielectric material and a columnar thin film.
