Frequency-independent parameters of an equivalent circuit of two dimensional island gold films

This paper deals with the outcome of a follow-up of our erlier work that tackled the ac measurements on two-dimensional island gold films [2D-I(Au)Fs] prepared by the thermal evaporation technique and identified by their stabilized surface resistivity (rho(s)) (23 MOmega/ to 37.5 GOmega/). In that work, the ac parallel resistance (r(p)) of the different 2D-I(Au)Fs was deduced, with the aid of a lock-in amplifier, as a function of the frequency (f) [0.1 to 80 kHz] of the voltage imposed on the films at six temperature points over the range 100 to 300 K. Here, the follow-up is intended to exploit the known values of r(p) at different frequencies in finding the magnitudes of the frequency-independent parameters of an equivalent circiut of 2D-I(Au)Fs. These parameters are R-b, R-g and C-g, where R-b is the resistance associated with the conduction within the bulk (interior) of islands, Rg is the resistance that accompanies the conduction across the gaps between islands and Cg is the capacitance due to the presence of metallic islands and gaps. The equation that relates r(p) to R-b, R-g, C-g and f is known and thus the experimental values of r(p) and the corresponding frequencies were inserted into it; then via a computerized analysis the least squares values of R-b, R-g and C-g were eventually deduced. It was found that: (i) R-b and R-g increase while C-g decreases with the increase in rho(s). (ii) R-b and C-g increases but R-g decreases with the increase in T. (iii) The activation energy of charge carrier generation increases as rho(s) does. (iv) The magnitude of the temperature coefficient of gap resistance increases with the increase in A and the decrease in T. The present results were interpreted, qualitatively, by assuming that the transfer of charge carriers, across the gaps between the islands, takes place via the thermally activated tunneling mechanism. To the best of our knowledge, the present results are the first to be reported for 2D-I(Au)Fs. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.