Model of conductivity of fullerite tubules in ion tracks of polymer foils

One of the possibilities to create sensors based on fullerite films is the incorporation of fullerite tubules in polymer foils. This paper describes first the production technology of such tubules with typically /spl sim/100 nm to /spl sim/3 /spl mu/m radius and /spl sim/10 to 25 /spl mu/m length. For this sake polyimide foils are irradiated by heavy ion beams and then etched. The thus created nanopores - the so-called "etched tracks" - are characterized by the ion transmission spectroscopy (ITS). Then fullerene is deposited layer by layer on the inner wall of these tracks, and both the reduction of the inner pore diameter and the resistance of the emerging fullerite tubules are determined. It is seen that no simple correlation exists between these two quantities. Therefore we established a simple analytical model in which the total tubule conductance consists of two components, a surface and a bulk conductance. The comparison of this theory with the experimental conductance data as a function of track radius by means of a least-square fit method indicates that the conductance of tubules with thin walls is essentially governed by surface conductivity whereas thick tubules rather can be described well by essentially the fullerite bulk conductivity. Numerical values of both the bulk and surface conductivities /spl sigma//sub bs/ ; /spl sigma//sub ss/ of the fullerite tubules are derived.