Abstract:
Thin metal films which contain nano-size pores yield higher than expected transmittance and larger than expected
times for transmission of near infra red radiation. An optically equivalent layer with complex refractive index (n*, k*)
can model measured specular transmittance and reflectance, when scattering is weak. The way surface plasmon effects
impact on these measured indices is considered. A strongly elevated n* is linked to trad the time for a surface plasmon to
re-radiate and hence delay transmission times, and reduced imaginary part k*, to resonant channelling via voids. Measurement
of n* thus allows an estimate of trad. The sensitivity of (n*, k*) to surface effects is illustrated using an insulating
overlayer to modify the surface states. Resultant measured changes in n*, k* are substantial. Results are for
two nanostructured metal systems characterised with 400,000· scanning electron microscopy.
