  Surface plasmon polaritons (SPPs) at the interface of a columnar thin film
(CTF) and metal exist over a range of propagation directions relative to the
morphology of the CTF which depends on the tilt of the columns in the CTF. The
phase speed of the SPP wave varies mainly as a function of the tilt of the CTF
columns. Both the confinement of the SPP wave to the interface and the decay of
the SPP wave along the direction of propagation depend strongly on the
direction of propagation relative to the morphologically significant plane of
the CTF. The greater the columnar tilt in relation to the interface, the
shorter is the range of propagation. Because of its porosity and the ability to
engineer this biaxial dielectric material, the CTF-metal interface may be more
attractive than traditional methods of producing SPPs.
