Admittance spectroscopy has been performed on Al dots deposited
on porous Silicon grown on p+ substrates. They exhibit d.c.
current-voltage characteristics of a metal-insulator-semiconductor structure
containing a large concentration of localized states in the insulator.
The admittance is composed of a frequency (ω) independent conductance
while the reactance varies as ωs with s = 1. This strongly suggests
that conduction through porous Silicon layers is governed by hopping
between surface states.