Generalized Theory of Electrical Conductivity and Current Noise for Discontinuous Metal Films Over a Wide Range of Temperatures

A complete discussion with an extension to the high temperature range of the main results of a recent theory on the electrical conduction and current noise in discontinuous metal films is given. In this theory the main conduction mechanism is a direct-tunnelling process of the electrons between metal islands within the insulator substrate. The tunnelling electrons must overcome a potential barrier which is temperature dependent. The model assumes that the electrons trapped in surface states can tunnel in the metal states giving rise to a double charge layer at the interface. The current noise is generated by a modulation mechanism of the carrier direct tunnelling due to thermal fluctuation of the potential barrier height, generated by a corresponding fluctuation of the surface charge. Experimental results for the conductivity and current noise behaviour on Au film deposited on sapphire tube are also given up to a temperature of about 950 K, and interpreted on the basis of the above theory.