Electrical conduction and current noise mechanism in discontinuous metal films. I. Theoretical

Abstract

A new model of conduction mechanism in discontinuous metal films which gives the temperature dependence of conductivity over a very large temperature interval, from -250 to 450\ifmmode^\circ\else\textdegree\fi{}C, and explains the origin of the conductivity fluctuations responsible for the current noise in these films is presented. It is shown that the conductivity change with temperature is due to a shift of the position of the Fermi level at the surface of the insulator. This changes the height of the potential barrier which must be overcome by tunneling of the conduction electrons. Such a shift, required at each temperature to ensure electron thermal equilibrium, is generated by a partial depletion of surface donor states located on the insulator surface between metal islands. It is further shown that the fluctuation of the surface charge created by the ionization of the surface states modulates the height of the tunneling barrier giving rise to a corresponding modulation of the electrical conductivity originating the current noise typical of discontinuous films. In paper II the results of the theory are compared with experiments.