  Boron doped amorphous conducting carbon films show MI transition induced by
doping. In this paper we discuss the ac conductivity of the films, which lie on
the insulating side of MI transition. The ac conductivity data is analyzed as a
function of frequency as well as temperature for both real as well as imaginary
part of the conductivity data. The ac conductivity of these samples shows
enhanced interaction effect at low temperature. The conduction mechanism at
high frequency and at low temperature is due to the tunneling mechanism. At
intermediate temperatures and at moderate frequencies, the conductivity data is
in good agreement with extended pair approximation modified for interaction
effect. At high temperature and at low frequencies, the mechanism of ac
conductivity is similar to that of dc conduction. The conductivity data for the
insulating samples near the boundary of MI transition were analyzed using an RC
element model. While fitting the impedance data, a new type of constant phase
element (inductive instead of capacitive) was found to be appropriate. At
present the origin of this inductive CPE is not is clear but we believe its
origin is in the electron-electron interaction, which makes any attempt of
applied frequency a slower response. Our ac conductivity results are well
explained by tunneling models rather than hopping models.
